Central highlands science roadshow resource booklet 2015

Central Highlands

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Central Highlands SCIENCE CENTRE SCIENCE ROADSHOW Resource Booklet 2015

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INTRODUCTION

Central Highland Science Centre’s travelling exhibition, “The Science Roadshow”, is designed to take the excitement of interactive science to everyone, no matter where they are! The Science Roadshow consists of 14 hands-on exhibits that explore the principles of light, music, sound, force, motion, electricity and magnetism.

We have produced this comprehensive resource booklet to better enable teachers to plan and incorporate “The Science Roadshow” visit into student learning programs. Our overarching objective is to spark children’s natural curiosity through free play.

Watch people of all ages turn themselves into a battery, crank up a tornado in a bottle, predict the outcome of chaos and much, much more.

We truly appreciate your support in ‘Inspiring Young Scientific Minds’ and we sincerely hope you enjoy the experience!

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Hints for teachers and helpers – during the visit and at home

Symptoms of a kid who loves science:

Thank you for helping students to learn during their visit to the Central Highlands Science Roadshow.

£ Likes experimenting and trying things out

What is the Central Highlands Science Roadshow?

The Central Highlands Science Roadshow plans to travel through the region teaching children about science. We would like to give students learning experiences that they would not usually have at school.

Welcoming the science barrier A room full of exhibits can be daunting to the non-scientist and you may feel unqualified to assist students with their understanding of an exhibit when you don’t understand it yourself. However, you don’t need to know any of the science yourself.

Instead, consider this approach. £ Stand alongside students who are experimenting with an exhibit. £ Show some interest in the exhibit and ask the student(s) what it does. £ You might like to try asking a question, then: £ Pause (wait for an answer)

£ Shows curiosity about the natural world £ Takes things apart and rebuilds them £ Asks lots of questions about why things are the way they are.

Science at home £ Spend time with your child pulling things apart to find out how they work, or building things like kit set radios.

For even more fun, try engaging your child in real=life science experiments at home. You can find good ideas on the internet, and many toy shops sell relatively cheap experiment sets. £ Take advantage of what’s out there in the community. Visit your local library to find books about science. Play with interactive displays and exhibits at places like museums and planetaria. £ Develop a love of reading in your child – it builds a love of knowledge. £ Maths is the basis of all science, so make it fun, encourage it.

£ Praise (tell them they did well)

£ If a child asks a question, don’t be afraid to say you don’t know but, importantly, show them how they can find out; do it together.

£ Tell them you don’t know about it yourself, but you want to know and you are relying on them to be the expert.

£ Latch onto opportunities whenever your child displays interest, and give practical and real examples of things.

£ Encourage them to investing and try things.

£ The natural world is usually a child’s first interest; it helps if parents are a little ‘wide-eyed’ too.

£ Prompt (give them a hint)

The first level of understanding may simply relate to ‘make things happen’ on the exhibit. £ Get them to tell you what they have found and show you how it works. Use questions to encourage them to investigate further. What science is it showing? How do we use this in real life? £ Ask them what the context board (the instructions board beside or on the exhibit) says. Assist the students to read it and repeat back to you what it means. £ By these simple steps you will encourage active involvement and learning ownership by the students which will carry forward as they move onto other exhibits.

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M U L U D N E P C CHAOTI Things to try £ Gently push the pendulum and watch it swing £ Gently push the pendulum again. Can you make it swing the same way? £ Can we control and predict how the pendulum will swing?

Exhibit message Magnets can repel each other if matching magnetic poles are placed side by side. This can create a ‘levitation’ effect.

The pendulum’s strange, chaotic movement is caused by magnets. Four magnets on the table top repel the magnet in the pendulum to make it swing this way. A small change in the way you swing the pendulum can affect the swinging pattern and where the pendulum stops.

Want to know more about magnets?

There are three main types of magnets: permanent magnets, temporary magnets and electromagnets.

Permanent magnets Once magnetised these magnets retain their level of magnetism. The earliest known magnet is ferric ferrite (lodestone). Ferric ferrite is a natural magnet that can be used to magnetise other materials including steel. For example, you can create a compass needle by rubbing a steel needle with ferric ferrite.

Steel can lose its magnetism by shock or the presence of other magnetics close by, so other materials are used to make more modern, stable magnets. For example, the powerful neodymium magnet, is made of a combination of neodymium (a rare earth metal), iron, and boron — Nd2Fe14B.

Temporary magnets These act like a magnet only when they are in a strong magnetic field.

Soft iron and certain iron alloys, such as permalloy (a mixture of iron and nickel) can be very easily magnetized, even in a weak field. These materials make excellent temporary magnets that are used in telephones and electric motors.

Electromagnets These magnets require an electric current to function. The simplest electromagnet has an electric current flowing through a copper wire coil called a solenoid. The direction of the current flow determines which end of the solenoid becomes the north and South Pole, and the magnitude of the current determines the strength of the electromagnet.

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Extra for experts Electromagnets can be used to develop high speed transportation vehicles such as Maglev trains. Maglev trains are suspended over the guideway (track) by magnetic repulsion, and propelled by changing magnetic fields. Once a train is pulled into the next section the magnetism switches so that the train is pulled on again.

The trains do not need engines, and do not burn fuel. Instead they use electric power fed to metal coils located on the guideway.

The major advantage of Maglev trains over conventional ones is that there is no friction between the train and the track.

Therefore, Maglev trains have the potential to be as fast as commercial aircraft (500 km per hour). The lack of friction between the train and the guideway also means that the train will need less maintenance.

There are two main types of maglev technology:

Electromagnetic suspension Electromagnets on the bottom of the train are oriented to the steel rail below. This system uses traditional electromagnets and requires a power source for the coils to conduct electricity.

Electromagnets and the coils only conduct electricity when a power supply is present.

Electrodynamic suspension This system uses permanent magnets. The repulsive force between two magnetic fields on the train and the rail levitates the train.

Scientists in Japan are using super- cooled, superconducting electromagnets on the guideway. The drawback of this approach is expense of the system required to cool the coils.

The first Maglev train in operation was the Shanghai Transrapid in China. This train travels from the city’s centre to the Pudong airport. It runs at a speed of 430 km/hr and the journey takes less than 8 minutes as opposed to an hour- long taxi ride.

Finding the science in your world The study of chaotic ‘movements’ in nature helps us to understand weather patterns and changes.

Quick fact Every single material and living creature on earth is magnetic.

However, the field is very weak. It’s possible to levitate living animals providing you have a magnet that is 100 to 1000 times stronger than a household magnet.

Scientists from the Nijmegen High Field Magnet Laboratory have safely levitated a living frog.

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Classroom activity Magnetic fish

Questions

In this activity students will explore general properties of magnets.

£ Which materials are magnetic?

Materials £ Horseshoe/Bar magnets £ Paper clips £ Steel washers £ Non metallic objects (matchsticks, rubber bands, twist ties, plastic etc. ) £ Aluminum foil £ Cardboard £ Scissors £ Markers £ Sticky tape £ String

£ How far away to the materials have to be from the magnet for it to attract them? £ Can you move the fish without touching them? (hint: put the fish onto a wide piece of cardboard) £ What magnetic items can you find at home?

Temporary magnets In this activity students will make their own magnets.

Materials £ Bar magnets £ Nails £ Steel washers £ Steel paperclips

£ 2 litre ice cream containers (or an equivalent container)

Method

£ Cut out fish template

➊ T ry and lift the paper clips and steel washers using the nail. ➋ S troke a nail in one direction using the one end of the bar

£ Glue

Method ➊ Arrange your students into groups of three or four. ➋P aste the fish templates onto the cardboard and cut them out. Each group should have eight fish (this can be done before the class). If the class has time they can colour the fish. ➌ Stick a different object onto each fish. ➍ Put the fish into the ice-cream containers. ➎ Tie the string onto the magnet. Fish for the Fish!

magnet 15 times to turn the nail into a temporary magnet.

➌ Try and pick up the different objects using the nail. sing new nails each time try stroking them 5, 20, 30, 50 ➍U times.

➎ Try and pick up the objects with the nails. ➏ S troke a nail you have turned into a magnet back and forth with a bar magnet 10 times.

➐ T ry and pick up the objects with the nail.

Questions £ How many paperclips or steel washers can you pick up with the nail? £ Can you pick up more objects if you stroke the nail more times? £ What happens when you stroke the nail back and forth? £ For further explanation of the science in these activities see

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RAG D C I T E N G A M Things to try £ Let the pieces of aluminium pipe on the outside of the tube drop from the top. What do you notice about the way they fall? £ Which piece of pipe falls more quickly?

Exhibit message Halfway along the inside of the tube are some magnets.

As the pieces of pipe fall past the magnets, the magnets make small electric charges (electrons) flow in circular paths around the metal pipe. The circular flows are called eddy currents.

The eddy currents in the falling pieces of pipe have a magnetic field of their own which is repelled by the magnets inside the tube.

This slows their fall.

The piece of pipe with the slit in it falls faster because the slit prevents an electrical current flowing around the whole piece of pipe to create a large, strong eddy current. Less energy from the falling tube is converted to electrical energy (eddy currents), so it falls faster.

SCIENCE CENTRE Classroom activity Eddy Currents A magnet falls more slowly through a metallic tube than it does through a nonmetallic tube.

When a magnet is dropped down a metallic tube, the changing magnetic field created by the falling magnet pushes electrons in the metal tube around in circular, eddylike currents. These eddy currents have their own magnetic field that opposes the fall of the magnet. The magnet falls dramatically slower than it does in ordinary free fall in a nonmetallic tube.

Materials £ Neodymium magnet £ Non magnetic object, such as pen or pencil £ 90cm length of aluminium, copper or brass tubing large enough to allow magnet to pass through and walls as thick as possible £ 0cm PVC or other non-metallic tubing.

Method:

Finding the science in your world

£ Hold the metal tube vertically.

One of the most common application of eddy currents is in the brakes of some trains. During braking, the metal wheels are exposed to a magnetic field from an electromagnet, generating eddy currents in the wheels. The magnetic interaction between the applied field and the eddy currents acts to slow the wheels down. The faster the wheels are spinning, the stronger the effect, meaning that as the train slows the braking force is reduced, producing a smooth stopping motion.

£ Drop the magnet through the tube.

Did you know?

Eddy currents are often generated in transformers and lead to power losses. To combat this, thin, laminated strips of metal are used in the construction of power transformers, rather than making the transformer out of one solid piece of metal. The thin strips are separated by insulating glue, which confines the eddy currents to the strips. This reduces the eddy currents, thus reducing the power loss.

£ Then drop a nonmagnetic object, such as a pen or pencil, through the tube. £ Notice that the magnet takes noticeably more time to fall. £ Now try dropping both magnetic and nonmagnetic objects through the PVC tube.

Note: As the magnet falls, the magnetic field around it constantly changes position. As the magnet passes through a given portion of the metal tube, this portion of the tube experiences a changing magnetic field, which induces the flow of eddy currents in an electrical conductor, such as the copper or aluminum tubing. The eddy currents create a magnetic field that exerts a force on the falling magnet.

The force opposes the magnet’s fall. As a result of this magnetic repulsion, the magnet falls much more slowly.

Want to know more about eddy currents?

An eddy current is a swirling current set up in a conductor in response to a changing magnetic field. By Lenz’s law, the current swirls in such a way as to create a magnetic field opposing the change; to do this in a conductor, electrons swirl in a plane perpendicular to the magnetic field.

Because of the tendency of eddy currents to oppose, eddy currents cause energy to be lost. More accurately, eddy currents transform more useful forms of energy, such as kinetic energy, into heat, which is generally much less useful.

In many applications the loss of useful energy is not particularly desirable, but there are some practical applications.

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Things to try

Sumo wrestler

Can you balance the six loose nails on top of the one stuck on the table? None of these six nails should touch the table!

A sumo wrestler spreads his legs wide and crouches before he clashes with his opponent. By widening his support base and lowering his balance point, a sumo wrestler makes himself as stable as possible.

Hint: Try to make a ‘roof’ with two loose nails forming the top beam and four nails hanging down from the beam to make the roof. Things balance better

Exhibit message All objects have a centre of mass. Structures are much more stable when their centre of mass is located below their point of support.

Want to know more about the balancing nails?

If you look at a pitched roof (or a really simple triangular tent) you might get some hints! These roofs have a cross beam and then supports that come down at an angle to meet the walls. If you start with one nail representing a cross beam and then look at either end of the structure you should be able to use two nails at each end of the cross beam to represent the supports that go down to the walls. Think carefully about which way round you put the nails! Can you use the ‘head’ of the nail to ‘lock off’ on the cross beam?

Now you have one nail left - where can you put this so that it will stop the supports from rolling off? Again think of which way round you might put the head of the nail. Your roof is flat at the moment - pick the ‘roof’ up from the bottom cross beam - try not to hold it rigidly or it will not balance itself out - very slowly lift it up and then balance it on the seventh nail.

Wow! All objects have a centre of mass. If an objects centre of mass is above its point of support, then it said to be balancing.

For instance, when you stand up your centre of balance is (located between your belly button and your spine) is above your point of support (your feet and the ground they are standing on). You are balancing!

Structures are much more stable when their centre of mass is located below their point of support. These are said to be hanging. One way to get all of the nails to balance is described above.

This solution changes the nails from balancing nails to hanging nails: the balance point of the six sticks combined is located below the point of support.

Extra for experts Some examples of keeping the mass lower than the point of support.

Birds Watch a bird sitting on a power line. They prevent toppling by adjusting their balance point using the position of their tail and head.

Sports cars Engineers try hard to make a sport car as light as possible, and then add weight on the bottom; this way, the center of mass is nearer to the street, and the car handles better.

Pole Vaulters Pole vaulters need to get their centre of mass—their hips—over the highest bar possible. To do this they use a pole that has some flexibility. As the vaulters spring off the ground, the pole bends; then the vaulter inverts themselves and pushes off the pole as it unbends. A champion pole vaulter can push their hips ten centimetres over their top hand grip.

Parallel bars These are gymnastic apparatus with two parallel bars that are supported with a steel frame. The gymnast swings between them and performs a hanging and swinging routine with flips and turns.

In 2002 scientists studied American and Japanese gymnasts and discovered that best gymnasts displayed a greater ability to lift their centre of mass during their routine. They also had greater backward horizontal motion of their centre of mass.

This study and many others show that the all the best gymnasts are better at moving their centre of mass to perform flips, twists and turns!

Classroom activity Bending and balancing Stand with your back against a wall. Make sure that the back of your feet are also against the wall.

Now bend forward. Can you bend forward without falling over? In order to keep your balance, your centre of mass must be above your feet. As a result, you fall over! Normally, when you bend over you move part of your body backwards at that same time so that your centre of mass stays above your feet.

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How it works Balance the stick on your fingers and compare the balancing point to the middle of the stick.

Things to try Balance the stick on your index fingers. Slide your fingers towards each other until they touch and the stick stays balanced. Do your fingers always meet at the same point on the stick?

Exhibit message The centre of mass can sometimes be found by balancing an object on your finger.

years of practice, but part of it is also that they carry a long pole with them. Unaided, a person’s center of balance is located just beneath their ribcage, about halfway from the ground to the top of a person’s head. This means that we balance from this part of our bodies. Carrying a long pole lowers our center of balance, just as holding out our arms to the sides does. If the pole is long enough, a person’s center of balance can be lowered to their knees, ankles or even the tops of their feet. A lower center of balance makes it easier for anyone to balance while walking across even a narrow rope.

Classroom activity Balancing Broom

The point where your fingers meet is called the balance point.

One finger tends to support the stick’s weight and moves less.

Your other finger supports less weight (giving less friction), so it slides more easily along the stick.

Materials

What is “center of mass”?

➊ F ind a smooth, flat hard floor. ➋ T ake the broom by the long handle and position it so

Gravity is the force that pulls objects toward the center of the Earth. An object’s center of mass (or gravity) is the average location of the weight of the object.

If you have a wooden ruler you can balance it on your finger at the 6 inch mark. The ruler has a uniform shape and its weight is evenly distributed along its shape. It is easy to determine that the 6 inch mark, right in the middle, is the center of mass (or gravity) for the ruler. There is an equal amount of weight on each side of the 6 inch mark; the gravitational pull on both sides of the rule is equal – so the ruler will balance.

If you have an object like a person trying to balance on a balance beam, then it is a little trickier to figure out where the center of mass (or gravity) is located. It will be a little different for each gymnast depending on how their weight is distributed on their body. Each gymnast learns the location of their own center of gravity and knows to keep that point centered over the balance beam. If that point is not centered, the gymnast will fall off.

£ Broom

Method

that it is standing up right with the bristles on the floor.

➌ T ry to get the broom to stand all by itself by making slight movements back and forwards with the handle. ou may want to pick the broom up and place it back ➍Y on the floor several times try to adjust the balance and weight equally.

➎ T his can take several attempts and patience. You may even want to try using a different broom if you find it a real struggle to get it to become balanced.

➏ T his is an amazing force of gravity experiment. I could not believe that a broom could actually stand up on its own.

The trick is to get the balance just right, which is called the center of gravity, and the broom will stand by itself.

Immobilize someone with your pinky finger Materials

Finding the science in your world

£ Chair

For our bodies to stay balanced, we must keep our balance point above our base of support. When we walk, we tilt out body so that our centre of mass is above the foot we are walking on.

Method:

Sumo wrestlers defend themselves against moments of force by being as stable as they possibly can be, and by using their centre of mass. Their centre of mass is where most of the mass of body is concentrated. For a sumo wrestler that’s really low down on their body, especially when they crouch down with their thighs and bottoms and huge tummies almost touching the floor. By taking this stance they have made their moment of inertia (measurement of the difficulty in changing the speed and direction of an object) as large as they possibly can.

Tight rope walkers make balancing while walking across a rope seem effortless. Even if the rope is hung over a deep canyon or a tank full of sharks, tight rope walkers seem to glide along from one side to the other without ever slipping or losing their footing. Of course, part of this is due to their

£ Volunteer

➊ T ell your volunteer to sit in the chair, with his/her back against the back of the chair and hands in lap. lace your pinky finger on his/her forehead. (You can use any ➋P finger- it does not have to be the pinky.)

➌ T ell your volunteer to stand up. Use your finger to keep his/her head from tilting forward. our volunteer will probably not be able to stand up. ➍Y hen you are standing, your center of mass (somewhere in ➎W your abdomen) is directly over your feet. When you are seated, your center of mass is above the seat of the chair, not over your feet. In order to stand up you need to move your center of mass from over the chair to over your feet. To accomplish this, you need to lean forward. Strangely enough, the amount of force needed to keep someone from leaning forward is not all that much. You can exert this force with one finger.

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How it works

Newton’s second law

Place one wheel on the top of one ramp, the other wheel on the top of the other ramp. Let go of both wheels at the same time.

Acceleration is produced when a force acts on a mass.

The greater the mass (of the object being accelerated) the greater the amount of force needed (to accelerate the object).

Things to try

What does this mean? Everyone unconsciously knows the Second Law. Everyone knows that heavier objects require more force to move the same distance as lighter objects.

Which wheel wins the race to the bottom?

Exhibit message To start something moving you need to give it a push or a pull.

More force is needed to get a heavy rock moving compared to a soccer ball. The rock resists a change to its motion more than the ball. The rock is said to have more inertia than the ball.

The inertia of wheels depends on two things; the mass of the wheel and where the mass is located. The wheel with its mass concentrated close to the axis has less inertia than the wheel with its mass away from the axis. As the force of gravity starts the wheel with its mass close to the axis rolling downhill, it rolls more quickly and wins the race.

Want to know more about the laws of motion?

Sir Isaac Newton was one of the greatest scientists and mathematicians that ever lived. Newton had new ideas about motion, which he called his three laws of motion. He also had ideas about gravity, the diffraction of light, and forces.

Newton’s third law For every action there is an equal and opposite re-action What does this mean? This means that for every force there is a reaction force that is equal in size, but opposite in direction.

That is to say that whenever an object pushes another object it gets pushed back in the opposite direction equally hard.

Finding the science in your world Wheels can be designed to make them easier to turn or harder to stop. For example, flywheels on cars with most of their mass near the outside rim are used to keep things turning due to their greater inertia.

Classroom activity Motion Quiz ho was the scientist who gave us the Laws of Motion? ➊W

Newton’s first law – The law of inertia An object at rest will remain at rest unless acted on by an unbalanced force. An object in motion continues in motion with the same speed and in the same direction unless acted upon by an unbalanced force.

What does this mean? This means that there is a natural tendency of objects to keep on doing what they’re doing. All objects resist changes in their state of motion. In the absence of an unbalanced force, an object in motion will maintain this state of motion.

ow many Laws of Motion are there? ➋H hat is another name for the first law of motion? ➌W hich law explains why we need to wear seatbelts? ➍W hich law says that force is equal to mass times ➎W acceleration (F=MA)? hich law says that heavier objects require more force ➏W than lighter objects to move or accelerate them? hich law explains how rockets are launched into space? ➐W hich law says that for every action there is an equal and ➑W opposite reaction?

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E C A R R E L L O R Things to try?

Have a rolling race between a ring, flat disc and ball to explore rotational inertia. Stand all shapes on their side behind the gate. Raise the gate to start them rolling at the same time.

Which shape will win a rolling race – the ring, the disc or the ball?

Exhibit message Objects need a force (such as a push) to start moving. Heavy things that need a stronger push have more inertia. Round things can have their mass spread far away from their turning point or axis. They take more effort to start rolling at first and have more rotational inertia.

Which shape will win a rolling race-the ring, the disc or the ball? (These shapes all have the same diameter and mass.)

Stand them all up on their side behind the gate. Raise the gate to start them rolling at the same time.

Why does the ball win the race ahead of the disc and the ring? While each shape has the same size and mass, each one has its mass spread in different areas. This is important for how easily each shape rolls along (‘rotational inertia’).

Things need a force (such as a push) to start moving. Heavy things that need a stronger push have more inertia.

Round things (such as the ring) can have their mass spread far away from their turning point or axis. They take more effort to start rolling at first and have more rotational inertia. The ball has most of its mass near its centre (turning axis). This gives it less rotational inertia, so it starts rolling quickly (and wins the race).

Making the rims of racing bike wheels lighter reduces their inertia and makes them easier to turn.

Want to know more about downhill racing?

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The amount of rotational inertia depends on mass and the distance of the mass from the rotational axis. The exact effect of these two things depends on the shape of the object, but in general, any object with its mass concentrated farthermost from its axis of rotation will be ‘the laziest’ roller.

In the race you started, the ring has the most inertia because its mass is concentrated away from the axis of rotation.

Extra for experts Distribution of weight around the axis of rotation is an important consideration in nature and industrial design.

For similar mass distributions, short legs have less rotational inertia than long legs. This is why a Chihuahua dog is able to run much more easily with quick strides than an Afghan hound.

Why do you find it easier to run when you bend your legs?

You guessed it. Bending your legs brings them closer to their axis of rotation and so reduces their rotational inertia.

If you were to trim some weight of your bicycle wheels so that it’d be less work to pedal, would it be better to take the weight from the rim or the hubs? Again, you guessed it. Removing weight from the rim is best. Why? Because the amount of rotational inertia increases with the distance of the mass from the axis of the rotation.

Finding the science in your world Making the rims of racing bike wheels lighter reduces their inertia and makes them easier to turn. Sometimes, mass is mostly placed on the rim of a wheel, so it will turn with greater force for a longer period of time, such as giant flywheels used in factories.

Classroom activity Which egg is which?

Do you ever feel like having a long sleep-in on Sunday morning? It could be said that you are resisting any change to your state of rest. Likewise, if you were hurtling down a steep hill on your bicycle, you would keep going until Whoops! Craaash! something stopped you. In either case, you are experiencing inertia - the tendency of moving objects to keep moving, and the tendency of stationary objects to stay stationary unless they are compelled to stop or move by force.

Materials

When you watched downhill race, you saw a special case of inertia called rotational inertia or the fact that rotating objects tend to keep rotating, while non-rotating objects tend to stay non- rotating.

➋ T he raw egg does not spin as easily - the liquid inside

£ Hard boiled egg £ Raw egg

Method

you tell which egg is hard boiled and which is raw? ➊ Can To find out which is which, spin a hard-boiled and a raw egg on their sides. The hard boiled egg spines faster and longer - inside it is hard and the contents spin with the egg. moves a different way to the shell, slowing it down.

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Things to try

£ Hit the bottles with a stick to make a sound. Which bottle makes the highest note? £ Which bottle produces the lowest note? £ Blow across the top of the bottles. Which bottle makes the highest note now?

Exhibit message Hitting the bottle makes the glass and water vibrate. These vibrations make a sound.

The bottle with the highest water level vibrates slowly to produce a low note. The bottle with the lowest water level vibrates quickly to produce a high note.

Blowing across the top of a bottle makes air inside vibrate to produce a sound. The air in the bottle with most water vibrates quickly to produce a higher note.

Want to know more about musical instruments?

The sounds that we hear around us, are the result of sound waves travelling through air. A sound wave is a wave of energy created by the disturbance of air around a vibrating source.

A sound is the brain’s interpretation of the ear’s detection of sound waves.

There are several different types of musical instruments and they create sounds in different ways.

Pipes There are two types of pipe instruments. They are brass and woodwind.

In woodwind instruments, such as a flute, the player blows over or on a mouthpiece which vibrates air down the air column. The pitch of the instrument depends on the length of the pipe. Long pipes produce lower pitched notes. Players can vary the pitch of the instrument by blocking and unblocking holes down the length of the pipe.

In brass instruments, such as the trumpet, the player creates the sound vibrations by pursing their lips and ‘blowing a raspberry’. Valves and slides are used to make the instrument longer and shorter to vary the pitch.

Strings Plucking a string forces it to move up and down quickly, that is, to vibrate. The speed of the vibration is called the frequency.

The frequency of a vibrating string depends on its length.

A short string vibrates faster (has a higher frequency) and therefore produces a high pitched note. When you pluck a long string, you get a low note. When you halve a sting’s length, the frequency doubles.

Although you hear a single note when you pluck the string, many different frequencies are present. This is because a string usually vibrates at many different frequencies at the one time.

Percussion instruments Percussion instruments do not usually produce notes of definite pitch and are mainly rhythm keepers.

There are several types of percussion instruments. Drums are membranophones as produce sounds by vibrating a stretched skin (membrane) over a cavity.

Percussion instruments that vibrate the entire body, such as xylophones or triangles are known as idiophones.

Extra for experts The Musical Bottles are instruments that you can make at home. Which of the following items do YOU consider to be musical instruments?

Humming Earth In 1988, Japanese scientists discovered that the Earth emits a deep, low-frequency rumble, which they called the ‘Earth’s hum’. The humming signal is only a few millihertz, which is much, much lower than the lowest tone humans can hear or

feel. It is thought that the humming may be caused by the Earth’s stormy seas.

Whistling language

Whistling is normally considered a form of musical expression.

However, for the people of the island of La Gomera in the Canary Islands, whistling is their language. This rare and endangered language is called Silbo Gomero.

Studies have shown that language- processing areas of the brain are activated when ‘speakers’ of Silbo Gomero hear their whistled language, but not when non-speakers hear it.

Brain symphony Scientists recorded the brainwaves of a person listening to music.

During a concert in Sydney in 2004, musicians turned these recorded brainwaves into new music.

Using the same brainwave data, each musician created a different musical interpretation of the ‘sound of the brain’. One of the musical pieces was described as sounding like a ‘blowfly hitting a chandelier’, while others sounded more like traditional music.

Mobile music In Austria in 2001, musicians used the audience’s mobile phones to create music. Audience members were assigned a certain ringtone and seat number upon arrival. During the performance, the musicians on stage triggered the mobile phones via a computer, creating music that cascaded through the crowd.

Try playing Happy Birthday on your mobile phone: 1121#6 1121#611##841 ##6421

Singing flowers We have always appreciated flowers for their beautiful colour and smell.

Now we can also love them for their ‘singing’. Technology from Japan has transformed flowers into speakers that can play our favourite songs.

A magnet and coil in the base of a vase connects to the stereo, transferring sound from the vase up the plant’s stem and out its petals!

Vegie tunes

Can you play a tune on a pineapple?

New Zealand-born Australian musician, Col E Flower, has created an entire band of instruments out of common fruits and vegetables. To play the ‘vegetable trombone’, he uses a sweet potato with a hole drilled in it and a stalk of celery for the slide.

Finding the science in your world Wind instruments such as trumpets or clarinet use keys and valves to lengthen or shorten the amount of space in which vibrations can occur. Pressing valves to minimize air space inside the tube creates a high pitched note, while releasing valves to maximize air space inside the tube creates a low pitched note.

Classroom activity Panpipes Materials £ Straws £ Scissors

Method

straws into lengths of 2cm, 4 cm, 6 cm and so on up to ➊ Cut 20cm in length. ➋ Lay them side by side, with their tops at the same level, and tape them together, Blow across the tops of the straw pipes as shown. Which pipe produces the highest note? Which pips makes the lowest note? ➌ As you blow across the top of a straw the air inside vibrates.

Longer straws have longer columns of air which vibrate more slowly and produce lower notes.

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EXHIBIT THONGAPHONE

Things to try Use the rubber shoe to strike the open ended pipes to play a musical tune. £ Which tube creates the highest pitch note? £ Which tube creates the lowest pitch note? £ How are these tubes different?

Even similar instruments such as a clarinet and an oboe playing the same note at the same volume sound different.

This is because instruments are made of different materials that affect the personality of their ‘voice’.

An instrument’s voice, known as timbre is also affected by its shape and how it’s played.

Exhibit message

Instruments make sounds by vibrating and different materials vibrate in different ways.

Sound is made when something vibrates. Slower vibrations produce lower pitched sounds. Faster vibrations produce higher pitched sounds.

Sounds have characteristic pitch (high or low note), loudness (a soft or loud volume), and sound ‘quality’.

Hitting the end of a pipe with a thong makes air inside the pipe vibrate to produce sound waves. Longer pipes produce longer sound waves (lower notes). Shorter pipes produce shorter sound waves (higher notes).

This principle is used in many musical instruments

Want to know more about percussion instruments?

Sound quality or timbre describes whether different sounds of the same pitch and loudness can be distinguished by how they sound (maybe clunky, tinny, soft, wooden, etc).

When we play a note on an instrument, it actually contains a number of different pitches. The main one is called the fundamental which is the note we hear. The other pitches are only present in a very small amount.

The thongaphone is a percussion instrument. These are any object that makes a sound by being struck, rubbed, scraped and shaken.

Each type of instrument produces different combinations of frequencies for the same note, which is one of the reasons why each instrument has a unique sound.

Percussion instruments are often split into two groups. These are;

If you want to hear a note that contains just the fundamental, just grab a tuning fork, strike it on the edge of a hard surface and hold the base on a solid object.

£ Instruments that make a definite pitch, and play a melody (eg thongapones); and £ Instruments that do not produce a definite melody. These instruments are usually used as rhythm keepers in a band.

Percussion instruments are almost as old as humanity.

Archaeologists believe that the first musical instruments - other than our voice - were our hands, feet, sticks, rocks and logs.

Classroom activity Clucking Cup Materials £ Plastic or paper cups £ String £ Small piece of fabric £ Water

Drums

Method

The oldest membrane drums (membranophones) are at least 5000 years old. The first ones were likely to have been made from skins of fish or animals stretched over hollow tree trunks.

ake a small hole in the bottom of the cup. Thread a length ➊M of string through the hole. Tie a note in both ends of the string so that it doesn’t slip out.

Membranophones have had many uses including religious rituals and communicating over long distances.

Bells Another type of percussion instrument that is used in religious rites is the bell. No one knows when they were first invented - the first evidence for them is in 4000 year old pictures from China.

Bells are also mentioned in the Old Testament of the Bible as part of Hebrew worship.

Some more unusual percussion instruments:

Juju belt This is a rattle from Ghana worn by dancers as a belt. The ‘rattles’ come from the ‘juju’ bean. Similar waist, arm and ankle belts are also worn for dancing in Nigeria.

Thumb piano This is a traditional instrument of the Zesuru tribes of the Shona people of Zimbabwe. The player uses thumbs to pluck the keys downwards and the forefinger to pluck the keys upwards.

Jaw harp The jaw harp is one of the oldest instruments in the world and is found in many countries. It is held in the mouth and plucked with the finger. Pitch is changed by changing the shape of the mouth.

Extra for experts When you listen to a symphony, you can identify different instruments.

➋ Hold the cup in one hand and slide the fingers of your other hand down the string. What do you hear? Wet a piece of fabric and hold it firmly around the string while you pull downwards. Do you hear a loud ‘clucking’ sound? s the wet fabric moves downwards, it grips the string a ➌A little, then slips a little, then grips again and so on. This makes the string vibrate. The vibrations travel up to the cup, making it vibrate too and producing a loud sound. What other sounds can you make? ➍ Design and make devices that produce sound effects. Try creating sounds of different animals, heavy rain, wind or thunder.

Musical straws Materials £ Straws £ Scissors

Method ➊ Cut one end of the straw into a V- shape. Put this into your mouth. Fold your lips over your teeth, bite down gently around the straw and blow! It may take practice to make a note. ➋ As you blow through the straw, the two V-shaped pieces of plastic vibrate very quickly. This causes the air inside the straw to vibrate and produce a sound. hat happens when you snip pieces off the end of the ➌W straw? As you make the straw shorter, the air inside vibrates more quickly and the note becomes higher. ➍ Try cutting small holes along the length of the straw. By covering and uncovering the holes you change the notes you make. Can you play a tune?

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EXHIBIT

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SCIENCE CENTRE

PIN PATTERNS

Things to try Make an impression! Create a 3D model! Use any object and your imagination to create a three dimensional art form.

How?

Exhibit message When the pins are pushed up, they reproduce the contours or shapes of the objects under them.

If the pins are then able to be locked in position, this reproduced shape can be retained and used to duplicate the original.

This method has been used in film to create visual special effects.

Want to know more about seeing in 3D? 3D means three-dimensional, i.e. something that has width, height and depth (length). Our physical environment is threedimensional and we move around in 3D every day.

Humans are able to perceive the spatial relationship between objects just by looking at them because we have 3D perception, also known as depth perception. As we look around, the retina in each eye forms a two-dimensional image of our surroundings and our brain processes these two images into a 3D visual experience.

However it’s important to note that having vision in both eyes (stereoscopic or binocular vision) is not the only way to see in 3D. People who can only see with one eye (monocular vision) can still perceive the world in 3D, and may even be unaware that they are stereo blind. They are simply missing one of the tools to see in 3D, so they rely on others without thinking about it.

Here are some of the tools that humans use for depth perception: Stereoscopic vision: Two eyes provide slightly separate images; closer objects appear more separated than distant ones.

Accommodation: As you focus on a close or distant object, the lenses in your eyes physically change shape, providing a clue as to how far away the object is.

Size familiarity: If you know the approximate size of an object, you can tell approximately how far away it is based on how big it looks. Similarly, if you know that two objects are a similar size to each other but one appears larger than the other, you will assume the larger object is closer.

Aerial perspective: Because light is scattered randomly by air, distant objects appear to have less contrast than nearby objects. Distant objects also appear less color-saturated and have a slight color tinge similar to the background (usually blue).

Extra for experts In order to represent the 3D world on a flat (2D) surface such as a television or movie screen, it’s desirable to simulate as many of these perception tools as possible.

2D Film & Video A traditional 2-D video image has width and height but technically it has no depth, that is everything in the image is presented at the same distance from the viewer. Still, the viewer does perceive the image as three-dimensional by subconsciously using the techniques listed above—much the same as how stereo-blind people perceive the real world.

3D Film & Video 3D video adds stereoscopic vision, meaning that two separate images are shown simultaneously—one to each eye. This presents enormous technical problems which is why there is still no perfect system almost 100 years since the first 3D movie was made.

Common display methods include: Anaglyphic processing (red/cyan glasses): The original 3D system, now largely out of favor.

Polarized light system (polarized filter glasses): The most common new system for cinemas.

Active shutter system (LCD shutter glasses): The most likely standard for the first generation of 3D televisions and other displays.

Parallax: As your head moves from side to side, closer objects appear to move more than distant ones.

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S N R E T T A P IN P

SCIENCE CENTRE

Finding the science in your world

Paper Mache Balloon

This technique is often used in modeling and to create visual special effects.

Materials:

Classroom Activities

£ Newspapers or paper for recycling

Salt Dough Fossils

£ White glue or papier mache paste

Materials:

£ Paint brush (optional)

£ Salt dough

Method

£ Paint

low air into a balloon until you reach the desire size. ➊B Remember a smaller balloon is easier to papier mache, especially for the younger student.

£ Paint brushes £ Dinosaur toys £ Cookie sheet £ Rolling pin £ Clear varnish spray

Method to make salt dough: ake about 1 cup salt and dissolve it in about 1 1/4 cup ➊T water (or a little more). ➋ Then stir in about 3 cups flour (one cup at a time), until it’s a nice soft dough.

How to make your salt dough fossils: ➊ Make salt dough according to the recipe in the link above.

Roll the dough flat with a rolling pin. ➋ Make one of the fossil ideas listed below, or come up with one of your own! Bake your fossil at 350 degrees for one hour. ➌ Once it is cool, you can paint the finished fossil. To preserve it, you’ll need to spray it with polyurethane or clear varnish spray.

Fossil Ideas: ress a dinosaur toy into the dough. Remove the toy to see ➊P the imprint or “fossil” left behind. ➋ Press the foot of a dinosaur into the dough to create a fossil. ➌ Press your child’s hand into the dough so that their hands mimic a three-toed dinosaur footprint.

£ Balloon

➋ Tear paper or newspaper into fairly large pieces. We need 3 layers of paper to cover our balloon. Newspapers are great to use because of how well they absorb the adhesive.

However, we suggest that to clearly distinguish one layer from the next, it’s good to alternate newspaper strips with unprinted paper. ake your adhesive or papier mache past by mixing ➌M approximately 2 parts white glue with 1 part water. ransfer some papier mache paste into a shallow tray. Dip a ➍T piece of paper into the paste and let the paper soak in the paste. hake off excess paste and lay the piece on the balloon. ➎S Smooth out the paper with your fingers.

this process, overlapping the paper pieces are you ➏ Repeat cover the entire surface of the balloon. You will find it easier and less messy if you set the balloon on top of a bucket or bowl as you work with your papier mache.

may also use a paint brush to smooth out the edge of ➐ You the paper pieces. ake a second layer. If you followed our tip about ➑M alternating the newspaper strip layer with an unprinted or coloured layer of paper, you will find it easier to finish a layer without missing any spots or over-layering certain areas. ake a third layer. ➒M et your papier mache dry completely. This may take ➓L around 2-3 days.

SCIENCE CENTRE RESOURCE BOOKLET 25

EXHIBIT HAND BATTERY

10

Things to try

Extra for experts

£ Put your hands on two metal plates. Does the pointer move on the meter?

Another type of electrical charge is called static electricity.

Static electricity is actually high voltage electricity, with electrostatic attraction and repulsion.

£ Which combination of metal plates gives the highest reading? £ Do the readings differ between different people?

Exhibit message Batteries contain two different metals and a paste called an electrolyte that conducts electricity. If your hands are salty with perspiration, they act like the electrolyte in a battery when you touch the metal plates. Together, you (as an electrolyte) and the metal plates make a battery.

When you lift your hands off the metal plates (made of copper and aluminium), you remove the battery’s electrolyte so the battery stops working. When you put your hands on the metal plates to create the battery, it makes a very weak electric current flow in a loop through your body and through the meter.

Want to know more about electricity?

Our explanation for electricity is that amazingly small particles called electrons move from one place to another.

This flow of electrons can have some immensely useful effects. Heating up the wire element of a jug, making gas glow in a fluorescent tube, generating the magnetic fields which make electric motors work are examples of where moving electrons are helpful.

To make electricity, electrons have to move. In the hand battery exhibit with which you made electricity, where did the electrons move? Electrons swap places in two main areas. They leap from one hand to the copper plate, and from the aluminium plate to your other hand. Like other types of batteries, your hands have acids, salts and moisture on them.

This chemically affects the metals. The copper sheet takes electrons from your hand, whereas the aluminium donates them to the other hand. Because electrons are moving off one metal plate and onto the other, a current is generated.

This is shown by the movement of the meter needle.

Electrons can be made to move from one place to another by a variety of energy sources. Magnetism (used in bicycle dynamos) and light energy (used in solar batteries) are two ways electrons can be forced to move.

High voltage can attract lint or tiny bits of paper and it can make hair stand on end.

High voltages create long sparks, crackling noises, blue glows and flashes. So, you can also see static electricity as lightning or as sparks when clothes cling to each other after being in a clothes dryer.

When you walk along carpet and then ‘zap’ someone with your finger, then you’ve actually been charging your body to several thousand volts.

Things that are ‘electrically neutral’ have negative electrons and positive protons that are very close together, so their charges cancel out.

But if some electrons are removed from their atoms, an area of positive net charge is created on the atom.

Static electricity is a fire safety hazard in many industries, including grain and chemical silos.

Products processed in these plant silos are very sensitive to discharges caused by the build-up of static electricity.

Silos have been constructed to withstand the effects of dust explosions by structural vents, shock resistant construction and isolation of the silos from other parts of the factory.

Studies showed that fires started when powder particles ranged from 0.7 mm to several millimetres in size.

Smaller powder particles need less ignition energy (IE) to combust or catch on fire. Therefore, small particles of powder tend to combust more easily with static electricity sparks.

However, static electricity can also be put to good use. A new generation of skis and snowboards will be fitted with built-in electronic brakes that slow skiers down before their speed gets out of control.

On flat ice, electrodes induce opposite charges in ice surface, causing electrostatic attraction and increasing friction.

Classroom activity Make your own battery

Electrons can also be made to move by forcing two different types of metals to play tug-of-war. For example, aluminium and copper try to pull electrons from one another if they are connected. Unlike the usual game of tug-of-war, it’s a oneway contest. The copper always wins.

Materials

Different metals have different abilities to attract electrons.

For example, copper and gold are much better at attracting and holding electrons than magnesium or aluminium. This is why you will make a current on the hand battery if you put your hands on different metals. But if you connect two plates made from the same metal, you will not generate a current.

Method

Moisture, especially salty or acidic solutions, greatly assists the movement of electrons from one metal to another.

Finding the science in your world When batteries ‘leak’, they release the electrolyte contained inside the battery capsule. Batteries can also leak if they are left inside an appliance that has not been used for long periods of time. These electrolytes tend to be corrosive or poisonous and should not be touched with bare skin.

£ copper wire £ adhesive tape £ beakers £ scissors £ aluminium foil £ alarm clock £ wire strippers £ ruler £ salt £ jug of warm water ➊ To make the battery: strip both ends of each wire. ➋ Attach a foil square to one end of each wire by folding the foil over the wire. ttach the wire without foil to the positive and negative ➌A terminals of the clock. ➍ Tape the other ends of the wires inside the beakers. ape the third wire between the beakers. Each beaker ➎T should now have one foil contact and one wire contact.

two teaspoons of salt in warm water then pour it ➏ Dissolve into both beakers.

sure that the water reaches all four contacts ➐ Make

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EXHIBIT

11

LF E S R U O Y T I GENERATE

Things to try

Extra for experts

£ Turn the wheel as fast as you can. What happens?

As the demand for energy increases renewable energy will play an important role in supplying the worlds clean energy needs.

£ What is the name of the device that converts the kinetic energy into electrical energy?

The five renewable sources used most often are:

Exhibit message

Biomass

Although there are many kinds of energy in the world, they all fall into two broad categories: potential energy and kinetic energy. Potential energy is when energy has been stored up and is waiting to do things. Kinetic energy is when that stored energy is being used up, either to make things move or happen.

Is energy derived from plants and animals. Biomass comes in many forms, the most common being wood. When we use plants as a source of energy we are converting their stored energy from the sun. Using the methane gas given off by landfills and animal waste is also becoming more common. Another increasingly popular form of biomass is in the form of biofuels such as ethanol and biodiesel, which is also derived from plants and animals.

Turning the handle creates potential energy. The potential energy is used up, or converts to kinetic energy when it is able to flow through the generator and electric circuit. The flow of energy, or the electric current, around this circuit is what is involved in powering the light bulb.

Electrical power is measured by both voltage and current.

The bigger the voltage and the bigger the current, the more electrical power you have. We measure electric power in units called watts.

Geothermal Uses heat generated by the earth’s interior. By drilling down into the Earth’s crust, much like we drill for oil, we can use that heat to generate electricity. Geothermal is a good source for heating homes and buildings.

Water

Watts = Volts x Amps

The energy contained in running water can be turned into electricity.

Water, which is impounded or held behind a dam, is released through a turbine that spins a generator producing electricity.

Voltage

Wind

The following equation can be used to measure watts:

The voltage is a kind of electrical force that makes electricity move through a wire and we measure it in volts. The bigger the voltage, the more current will tend to flow. For example, a 12-volt car battery will generally produce more current that a 1.5-volt flashlight battery.

Current Voltage does not, itself, go anywhere: it’s quite wrong to talk about voltage “flowing through” things. What moves through the wire in a circuit is electric current: a steady flow of electrons, measured in amperers (or amps)

Power Electrical power is measured in watts.

As the wind blows it spins the large blades on a wind turbine and generates electricity.

Solar The energy from the sun can be converted into heat and electricity.

Sunlight can be captured using photovoltaic cells which convert the sun’s energy into electricity.

Currently only hydropower is widely used as an energy resource, while the other four types of renewable energy are not commonly used as primary energy sources. Reasons for their restricted use include the cost of specialty materials (e.g. photovoltaic panels are expensive to produce) and the fact that it can be difficult to distribute the power they generate.

The speed of the handle being turned directly affects how bright the light bulb will shine. The greater the speed, the higher the voltage and the more current will tend to flow through the circuit and the filament (thin piece of wire inside the bulb) making it heat up and give off light.

Finding the science in your world

Want to learn more about how electricity moves in a circuit?

Now we just have to flip a switch or plug in a cord!

A current of electricity is a steady flow of electrons. When electrons move from one place to another, round a circuit, they carry electrical energy from place to place like marching ants carrying leaves. Instead of carrying leaves, electrons carry a tiny amount of electric charge.

Electricity can travel through something when its structure allows electrons to move thought it easily. Materials such as copper metals that conduct electricity (allow it to flow freely) are called conductors. Materials that don’t allow electricity to pass through them so readily, such as rubber and plastic, are called insulators.

Before we began generating electricity, fireplaces and pot-belly stoves kept homes warm, kerosene lamps and candles lit homes and food was kept cool in iceboxes or underground storage cellars.

Electricity however has to travel a long way to get to your house.

In fact, the power plant where your electricity is made might be hundreds of miles away!

All the poles and wires you see along the highway and in front of your house are called the electrical transmission and distribution system. Today, power plants all across the country are connected to each other through the electrical system (sometimes called the “power grid”). If one power plant can’t produce enough electricity to run all the air conditioners when it’s hot, another power plant can send some where it’s needed.

Classroom activity

For electricity to flow, there has to be something to push the electrons along. This is called an electromotive force (EMF). An electromotive force is better known as voltage.

Make your own lightning

Electricity can move around a circuit in two different ways: direct current (DC) or alternating current (AC). Direct current is electricity that flows the same way. Most toys and small gadgets have circuits that work this way. In alternating current, instead of always flowing the same way, the electrons constantly reverse direction – about 50-60 times every second.

This is more common in bigger appliance in your home such as the washing machine.

Materials:

Lightning is a huge electric spark that jumps from the clouds to the ground

£ Comb £ Piece of wool £ Metal door knob

Method ub the comb with a piece of wool. This charges the comb with ➊R electricity. ➋ Hold the comb near a metal door knob, which is uncharged. You should see a small spark because electricity is jumping from the charged object (the comb) to the neutral object (the door knob)

SCIENCE CENTRE RESOURCE BOOKLET 29

EXHIBIT

GEAR TABLE

12

Bevelled gears

Rack and pinion

Things to try Arrange all of the gears on the table so their teeth are interlocking. Slowly spin one of the gear wheels and watch what happens. £ Count how many times the other gears turn for each time the gear you are spinning turns once. £ Do the other gears spin at the same speed as the one you are spinning?

Exhibit message Gears are wheels with teeth. They are used in machines to make work easier. When a big gear spins a smaller gear, the smaller gear always spins faster, but with less force. The larger gear spins slower than the small gear, but with greater force.

Want to know more about gears?

Small gears turn faster than large gears. Here, the red gear (with 12 teeth) has half as many teeth as the blue gear (with 24 teeth).

The smaller red gear must turn twice every time the blue gear turns once. So, the red gear and anything attached to it will turn double the speed of the blue gear. This is called movement magnification.

If the small red gear drives the large blue gear, the blue gear will turn with twice as much force (or torque). This is called force magnification.

Bike gears of different size change the distance that the bike moves forward with each pedal stroke so you can cycle faster or go uphill.

Types of Gears Spur Gears Spur gears are meshed together. The teeth are carefully shaped to give a smooth transmission of power with little friction. These gears align side to side and are the ones used in this exhibit.

Bevelled gears Cooks use gears to whip up eggs for omelettes!

One turn of an egg beater’s handle turns one large gear. This large gear turns two smaller, angled gears and their whisks four times, which can be fast enough to whip eggs and cream.

Rack and pinion A round gear wheel (pinion) can push a kind of ‘flattened’ out gear (rack).

Rack and pinion gears let you turn a gear to push or pull something else in a straight line.

A bottle opener pulls a cork straight out of a wine bottle.

Which part of this bottle opener is the pinion, and which part is the rack?

Rack and pinion steering wheels in cars push the car’s wheels left or right as you turn the steering wheel.

Worm gears Worm gears are found in small electric motors and even on guitars for tuning strings.

Differential Gear

Worm gears

They have a normal round gear pushing around a screw-shaped (worm) gear.

Extra for experts Differential gears As a car drives around a corner, the wheel on the outside of the corner travels further and faster than the other.

A differential gear lets each wheel travel at different speeds so the car stays in control as it goes around a corner.

Each wheel has a separate axle and they are linked together by a set of gears.

When the car is going straight, both wheels turn at the same speed and the gears in the differential rotate at the same speed.

When you hold one wheel (or when the car goes around a corner) the two smaller gears (planet pinions) in the differential are forced to roll around the slow moving, larger inner gear (the sun gear) without turning it. This allows the wheels to turn at different speeds.

The origins of the differential gear are unclear. It is possible that they were used in several parts around the world in ancient times. The oldest known object with a differential gear is the Antikythera mechanism which has been dated to 150-100BC. It is an astronomical computer used to predict the movements of the moon, sun and potentially other planets. The Antikythera mechanism contained 37 gears, however only 30 have survived

Quick fact NASA scientists are developing tiny molecular gears that are one nanometer across. For reference, a pinhead is roughly a million nanometers wide! The scientists hope to use them to build tiny machines that could make aerospace equipment in atomic detail.

Finding the science in your world Many bicycles have gears to make it easier to ride up hills.

A car’s gearbox gets the car moving and it builds up speed.

Classroom activity Gears from Bottle Tops Materials £B ottle tops Method esign and make a gear system from bottle tops that ➊D will change a horizontal movement into a vertical turning movement. esign and build a model gear system that will reverse the ➋D direction of turning. esign and put together three different sized cogs so that one ➌D turn of the first cog will turn the third cog ten times. ake up some other similar challenges for other students. ➍M

SCIENCE CENTRE RESOURCE BOOKLET 31

EXHIBIT TANGRANS SOLUTIONS

13

Things to try

Classroom activities

How many shapes can you make from the same seven geometric puzzle pieces?

The tangram could almost be described as a reverse jigsaw puzzle, as the student begins with a complete set of pieces assembled together in a flat organisation. The idea is to them dissemble the pieces and rearrange them in such a way as to create the desired image.

Exhibit message This puzzle is called a TANGRAM puzzle. This is a spatial puzzle testing problem solving skills. Tangrams consist of pieces or objects that must be manipulated into a specific spatial configuration.

This Tangram puzzle originated in China possibly 4000 years ago.

Make your own Tangram Materials £ Ruler £ Pencil £ Felt-tip pen £ Eraser

Method raw a 4 or 8 inch square with your felt-tip pen. ➊D ou need to draw a grid of smaller squares onto your current ➋Y square. So get your pencil out and draw a 1 inch grid in the 4 inch square (if you chose an 8 inch square then draw a 2 inch grid). ou now need to draw the lines that will mark out the edges ➌Y of each tangram piece. These should be drawn darker than your grid lines. With the felt-tip pen, draw your first line from the bottom left corner to the top right corner, effectively creating two large triangles. reate another triangle in the top left corner. Start from ➍C halfway down your main piece on the left side and draw a diagonal line that meets the top of your square in the middle. raw a diagonal line from the bottom right corner of the grid ➎D through the centre of your first line and stop at your second line.

Want to know more about Tangrams and other spatial-logic puzzles?

Historians are unsure when Tangrams were developed. It is probable that they originated in China thousands of years ago.

Ivory Tangram sets appeared in Britain in the late 1700s and they were adapted into various other puzzles.

One popular adaptation of Tangram puzzles includes The Magic Egg. The magic egg is cut into segments which are used to create birds.

Tangrams can be used to model the Pythagorean Theorem.

Pythagoras was a mathematician who developed a formula for determining the lengths of the sides of right angled triangles.

He discovered that a2 + b2 = c2

our fourth line will join your first and second line together. ➏Y Draw a diagonal line from the point where your second line intersected the top edge. Draw through one square to the point where it meets your first line. It should meet the line at the bottom right corner of the grid square. ou should be able to see that you have drawn four clearly ➐Y defined triangles and one square. our last line should be drawn from the point where your ➑Y second and third lines meet (also the middle of your second line). Draw the line downwards on your grid until it meets your first drawn line. Rub out your lightly marked grid. ow your tangram set is completed, you should see 5 clearly ➒N defined triangles, a square and a parallelogram.

What numbers, letters, animals can you make?

Side ‘c’ is also called the hypotenuse

Extra for Experts A similar puzzle is Dudney’s Triangle. It involves cutting a square into several pieces, then rearranging them to make a triangle.

Finding the science in your world Working through puzzles like this can help to develop problem solving skills. When people solve puzzles and other problems, they may use trial and error, insight (mental manipulation of available information), or a technique that has worked in the past.

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EXHIBIT

34 SCIENCE CENTRE RESOURCE BOOKLET

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SCIENCE CENTRE

BLACKOUT Things to try

Finding the science in your world

£ What colour is the box painted inside?

If you peer into a dark room, you are unable to distinguish shapes and colours until light is used to illuminate the room and it reflects off the room’s objects, walls and ceiling and reaches your visual system.

£ D oes the colour change inside the box when you open the lid, allowing light inside?

Exhibit message Nothing has to leave your eyes for seeing to occur. We can see objects when light hits the object’s surface and reflects back towards our eye.

When the box’s lid is closed, the tiny amount of light inside the box is absorbed by the box’s lining or reflected back through the hole, so it appears black to your eyes.

When you lift the lid and let in lots of light, the box’s red lining reflects MOST of the light back to your eye so it appears red.

If ALL of the light was reflected, it would be a mirror.

Your eyes cannot detect this tiny amount of light, so it looks black. When you lift the lid, the inside surface of the block reflects MOST of the light back to your eye so it appears white.

Some coloured paints or surfaces are more effective at reflecting light. By selecting colours that tend to contrast more with their surroundings, or by selecting materials that are better at reflecting light (such as retroreflective materials), high visibility equipment can be created for safety on the road or within construction sites.

Quick fact Our brains work out how big an object is by using the angle of the light as it enters our eyes.

A telescope makes distant objects appear larger by bending this light. The light rays from a distant object change direction as they move through the lens and again as they leave. The eyepiece or the lens brings the image into focus.

If ALL of the light was reflected, it would be a mirror.

Classroom activity

If most of the light was absorbed, it would appear black, like the paint on the outside of the box.

Splitting Light

Want to know more about what you see?

The colour of illuminated things is the result of light reflection.

Unlike things such as television, the sun or coloured lamps which all emit light, to see objects such as the Blackout box, light must first be directed onto them so that it bounces back to our eyes.

The colour we see them as is partly determined by how much light bounces back.

While the top is closed, very little light enters and the coating of the inside of the box absorbs most of the light, which does enter.

Therefore, it appears black when you look through the peephole.

When you lift the lid, you flood the inside of the box with light.

Most of this light is reflected by the material, which coats the inner surface of the box. So, now it appears white.

Light is composed of different colours. A spectroscope is a specialized scientific devise that is used to split light into various wavelengths.

Materials £ Thick cardboard £ Straight drinking glass £ Water £ Paper

Method Make a long, narrow cut from the bottom of the cardboard to just about the height of the glass.

Sit the glass on the piece of paper in front of a window that lets in a lot of sun and place the cardboard between the glass and the window (remember to have the cut in the cardboard running the length of the glass).

You should see the light split into colours.

If the coating were to reflect all the light directed onto it and not just most of it, what colour would it appear to be?

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EXHIBIT COLOURED FILTERS

EXHIBIT SEEING COLOURS

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Things to try £L ook at the picture through the red filter, then the blue filter.

Do you see the same picture through each filter? £ How does each filter change what you’re seeing? £ I f we used a yellow filter, what would we see in the picture?

Exhibit message Coloured filters can be used to block out unwanted colours of light.

Blue filters only let blue light pass through. Red filters only let red light pass through. You can only see the red ink through the red filter, and you can only see blue ink through the blue filter.

Want to know more about coloured filters?

Rainbows, glass prisms and crystals show us that white light is not really white! It is a mixture of many different colours. Red, orange, yellow, green, blue, indigo and violet combined make white.

If you see ‘white’, you are looking at a mixture of all the colours of the spectrum. If you see ‘black’, you are seeing no light because all colours have been absorbed. You see ‘colour’ it is because your eyes can detect white light minus one or more of its components.

Light filters are designed to block one or more of the different colours which make up white light. The blue filter captures all the colours except blue which it allows to pass through. The red filter captures all the colours, including the blue light, but allows the red light to pass through. So, which set of pictures you see depends where the light travels before it reaches your eyes.

When you look at the pictures without the filters, each part of the poster absorbs or reflects some of the white light. The red ink absorbs all of the colours in the white light except the red part. This red light is reflected from the poster but if it passes through the blue filter, it is absorbed before we can see it as red. Instead it appears black. Only blue light can pass through the blue filter but you are unable to see the blue lines in the drawing because you cannot distinguish it from the background. The red filter does the opposite. It absorbs the reflected blue light and allows the red light reflected from the red ink and the white background to pass through. Through the red filter, you see the blue lines as black patterns on a red background.

Quick fact Thomas Young, an English scientist discovered in 1807 that a mixture of pure red, green and blue light produced ‘white’ light. These three colours are called additive primary colours.

Any two of them added produce an additive secondary colour. Any two of the additive secondary colours that add to make white light are called complementary colours.

Extra for experts Being able to combine the three colours—red, green and blue—to produce an extensive array of other colours is very useful. The combination effect is used on your television screen and to make colour pictures in books and magazines.

Your television screen is coated with thousands of tiny dots which glow red, green or blue when electron beams strike them. Your eyes do not see individual dots because they are very small and very close together. Rather than see separate dots, your eyes interpret combinations and intensity of just three different types of dot as a full range of different colours.

Similarly, colour magazine pictures are made using many tiny dots. As with television screens, red, blue and green (called the additive primary colours) are used in the form of dots to produce colour pictures.

Why is the sky blue?

The sky appears blue because all of the colours which compose white light, except blue, are scattered or absorbed by the gases which comprise the atmosphere. Can you think of a reason why the sky appears red at sunrise and sunset?

Finding the science in your world Coloured filters are used in photography and sunglasses to filter out unwanted colours of light.

Coloured filters are also used in theatres to create certain moods or settings. For example, blue filters may be used to create a night time scene, while yellow filters may be used to create a sunny day scene.

Classroom activity Coloured Shadows This activity should be done in darkened room Materials £ Torch £ Red, green and blue cellophane £ Tape £ White paper

Method ver the end of each torch, tape either a piece of red, blue or ➊O green cellophane. hine the torches onto a white piece of paper. ➋S Experiment with the positions of the three torches until each ➌ beam is focussed on the same spot. an you make white light from colours? ➍C

Coloured Filters You can make your own version of the Coloured Filters exhibit

Materials £ Blue and red coloured cellophane paper £ Blue and red pencils

Method sing blue and red coloured pencils, superimpose two ➊ U different drawings on a piece of white paper. iew the drawings through red cellophane and then blue ➋V cellophane. What do you see?

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EXHIBIT TORNADO IN A BOTTLE

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SCIENCE CENTRE Things to try

Classroom activity

£T urn the bottles upside down. Does the water flow slowly or quickly into the bottom bottle?

Vortex Rings

£T urn the bottles upside down again, but swirl the bottles a few times as the water begins to flow. Does the water flow faster or slower?

What do dolphins, humans and volcanoes have in common?

They can all produce toroidal vortices of course! Surprised?

Grab some food colour and a glass of water to find out how.

Exhibit message Pouring water between two connected bottles is most efficient if a vortex is generated.

When you swirl the bottles, you create a vortex with a hole.

The hole in a vortex allows air to move into the top bottle as water flows into the bottom bottle. Without the vortex, the water flows more slowly into the bottom bottle. A vortex can occur when air or water moves quickly from one place to another.

➊ F ill a tall glass to the brim with water and wait for at least 30 seconds. Even though it looks still, water keeps swirling for ages so the longer you wait the better.

HINT: Use an eye-dropper if your food colouring is not the squeeze bottle type.

Want to know more?

When any fluid (including air) moves around a central point, a vortex is formed. There are different types of vortices. Some that are probably more familiar are tornadoes or water swirling down the drain. But with all vortices, when the movement of a vortex slows down, it breaks up. The movement of these fluids during a vortex breakdown is not well understood, and is an area of constant research by engineers and scientists Ring-shaped vortices are also made in Nature by dolphins and even volcanoes. A volcano can sometimes emit a huge toroidal vortex of steam and gas. These can be up to 200 metres across and up to 1 kilometre high!

Because a fast moving aeroplane creates vortices as it travels, sometimes these vortices can breakdown and hinder the smooth flight of the plane. So, aeronautical engineers need to design planes that reduce the breaking down of these vortices. To do that, they experiment with planes in wind tunnels, which is just one way to research what causes these breakdowns (is it the curve of the wing or the shape of the tail?).

Combustion scientists, on the other hand, like to know how to make a vortex breakdown because it is a really good way for air and fluids to mix; making a better explosion!

Quick fact Mathematicians call the shape of a doughnut a ‘toroid’.

Physicists call a swirling fluid a ‘vortex’. A toroidal vortex, then, is a swirling doughnut of fluid.

➋ S queeze gently so a drop of food colour is dangling from the tip of the bottle. Touch the water surface with the drop.

ow! The drop of food colour ➌W shoots down into the water and almost instantly turns into a tiny little donut!

➍ L ook closely and you’ll see the donut is swirling in on itself as it descends. While it’s moving quickly, the ring is very stable and retains its shape.

s it descends and slows down, ➎A the donut suddenly becomes unstable and breaks up - it’s called a vortex breakdown. If your water was still enough, a beautiful inverted crown might form. The tips of the crown are even smaller vortex rings.

Finding the science in your world Tornadoes, cyclones and even a draining sink’s plug hole are naturally-occurring vortices.

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SCIENCE CENTRE Central Highlands Science Centre Inc. PO BOX 293 EMERALD QLD 4720 CALL 0487 193 627 EMAIL club@chscience.com.au www.chscience.com.au

Answers

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GRAVITY CROSSWORD Across: ramps, pressure, fall, cork, accelerates, fly, weight, pull, mass, floats, erosion

MOTION QUIZ ir Isaac Newton ➊ S ➌ Law of Inertia

➋ Three ➍ First Law of Motion

Down: stronger, forces, gravity, navel, triangle, arches, Jupiter, scales, balance

➎ Second Law of Motion ➐ Third Law of Motion

➏ Second Law of Motion ➑ Third Law of Motion

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ELECTRICITY WORD SEARCH

METEORITE CRATERS

The extra mystery words are: plug, lamp, electrons, generator, lightning.

1a. Becomes deeper.

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1b. Becomes wider.

1c. Flour is splattered more widely.

BOUNCING LIGHT AROUND

2. Yes.

Reflects, kaleidoscope, silver, image, mirror, periscope, magnified, pond. Reversed.

3. The hole is oval and the splatter is all away from the direction of the impact.

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4.

It shows how the surface and lower layers behave during an impact.

RAMP IT UP PUZZLE

5. Yes. By showing how all the parts work in miniature.

It removes guesswork.

An INCLINED PLANE is a simple machine with a flat surface whose end points are at different heights.

5 mystery words – distance, motor, load, screw, work