Global Thinkers: Technology and Digitalisation Stage I. Secondary (sample)

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Indenxowledge of the course Basic k

Challenges that LEAVE THEIR IMPRINT My best gift is you .............................................................................10

1 Technology and solving problems

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• Our relationship with the planet 1. Advances of humanity thanks to technology 2. Impact of technical activity 3. Environmental impact of technological activity 4. Technological problem-solving process 5. The classroom workshop and technology jobs Technology workshop. Signs in the classroom workshop Understand, reflect and test your skills

2 Object design and communication of ideas

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• Technology and drawing 1. Graphic communication, a universal language 2. Drawing supplies and materials 3. Freehand drawing 4. Scales 5. Projections and views of an object 6. Perspective 7. Reports in technology projects Technology workshop. Make a budget Understand, reflect and test your skills

3 Materials and manufacturing of objects

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• What do we make things out of?

1. Materials 2. Properties of materials 3. Wood 4. What do we use wood for?

5. Woodworking tools 6. Metal 7. Ferrous metals 8. Non-ferrous metals 9. Metalworking tools 10. Working with metals Technology workshop. Build a soundboard Understand, reflect and test your skills Portfolio. ............................................................................................... 82

2

Challenges that LEAVE THEIR IMPRINT We need clean energy ....................................................................84

Challenges that LEAVE THEIR IMPRINT Do you want to be good gamer? .............................................. 184

4 Structures and mechanisms

7 Virtual learning environments

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• Telecommunications and VLE

• Structures everywhere 1. Structures 2. Forces 3. Structural components 4. Types of structures 5. Beams 6. Mechanisms Technology workshop. Lightweight structures Understand, reflect and test your skills

5 Electricity

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1. The virtual environment 2. Moodle environment 3. Teams for virtual learning 4. Cloud storage 5. Online office suites Technology workshop. Hold a conference call with Jitsi Meet Understand, reflect and test your skills

8 Introduction to programming

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• Programmable machines

• Our day-to-day energy 1. Electric circuits 2. Electric generators 3. Conductors and insulators 4. Electrical loads 5. Control and protection elements 6. Electronic symbols 7. Electrical resistance 8. Circuit connections 9. The protoboard 10. The Tinkercad circuit 11. Energy sources 12. Generation and transport of electrical energy 13. Energy efficiency Technology workshop. Build an electric motor Understand, reflect and test your skills

6 Digital tools and devices

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• A programmable world 1. Computer components 2. Central processing unit 3. Peripherals 4. Operating systems 5. Application software 6. Text processors 7. Electronic presentations 8. Spreadsheets Understand, reflect and test your skills

1. Computer language 2. Programming with Scratch Technology workshop. Programme with Pseint Understand, reflect and test your skills

9 Programming and robotics

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• Automatic machines and robots 1.

2.

3.

4.

5.

Introduction to robotics Robot architecture Control systems. Sensors Programming robots. Crumble Programming robots. Arduino and compatible boards 6. Robotics starter kits Technology workshop. Assemble and programme a line-following robot. Programme a push-button traffic light for pedestrians Understand, reflect and test your skills Portfolio. ............................................................................................ 260

Portfolio. ..............................................................................................182

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Structures s m s i n a h c e m d an

A WORLD OF CONSTRUCTIONS

Structures are everywhere. Look around you and you’ll see all kinds of components that support objects. In fact, everything that needs to be held up must be supported by structures.

Some structures protect objects by surrounding them.

Other structures are internal; your skeleton inside your body, for example. There are also some objects which contain several structures: an outer structure that protects the internal parts, and an internal structure that supports the object’s own weight. Cars, trains, aeroplanes and many other means of transport have multiple structures for these precise reasons.

Structures are fundamental to developing housing, neighbourhoods, towns, cities and infrastructure such as power stations and power transmission, motorways, airports, railways and ports. These all allow people to travel and goods to be transported, as well as facilitating communication from any one place on the Earth to another. Not having good infrastructure can hold a country back, limiting how much it can develop.

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READING AND LISTENING

1 According to the text, what kind of structures can be found in the natural world and man-made environments?

2 What are these structures? Where would you find them? How do you think they are made? Do you think they are strong?

3 Look at the phrases ‘held up’ and ‘hold back’ in the text. Choose their correct meanings from the below options. a) supported; b) suspended; c) grow; d) inhibit.

GES THAT

SPEAKING

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Look at SDG 9 and target 9.a. What is infrastructure? Find a definition in an English dictionary, then discuss the questions below with a partner.

1 Would you say infrastructure in your country is good? Think about: roads

ports

electricity supply

transport

Internet

water

2 How does reliable and sustainable infrastructure benefit a country and help it develop?

3 How can poor infrastructure affect productivity in the developing world?

4 Why might landlocked or island states need more investment in infrastructure?

5 Look online for information about these technological advances in infrastructure.

How could they improve productivity and development? Could they link to any other SDGs? drones

high speed rail self-healing concrete green asphalt In my opinion, our transport system is excellent because…

I completely agree with you. I reckon it is useful for us because…

WRITING

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CHALLEN

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IR IMPRIN

E LEAVE TH

LEARNING SEQUENCE WE DESIGN THE MULTIPLIER PULLEY SYSTEM You must design a multiplier pulley system and calculate the transmission ratio according to the sizes of its pulleys to find out the speed gain you will achieve.

WE BUILD THE PULLEYS As it is going to take a lot of speed multiplication, it will be necessary to build two or three pulley systems to join them into a multiplier.

2.1 The easiest method to build them is to cut a circle of the desired size and two slightly larger ones to glue to the sides of the first.

The materials you choose should be light and easy to cut.

2.2 Remember to mark the centres of the circles well to put the axles. Also, keep in mind that it will be necessary to mount a small and a large pulley on some axles.

WE BUILD THE MILL AND CONNECT THE SYSTEMS TO OBTAIN A PULLEY TRAIN 3.1 Now we must connect the output of one pulley system with the input of the next. To transmit the movement, you can use a rope or an elastic band.

3.2 You must design and build the structure of the mill to be able to install the pulley train at its base.

Look at SDGs 9.1 and 9.a. Think about your school. Does it have reliable, sustainable, resilient, and quality infrastructure?

Write a letter to the local council recommending an improvement the school could make to its infrastructure to become more sustainable and reliable.

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STRUCTURES

A structure is an object with one fundamental function, to support loads. It has to keep these loads fixed in their place within it or hold loads in place on top of it. Let’s take a house as an example. Its function as a structure is to shelter the people who live in it along with their possessions. Other structures are designed to help us cross potentially dangerous landscapes in the natural world, such as a bridge built over a river or deep ravine. Architects and engineers have to consider three essential conditions when they design a structure:

• A structure must be stable, it has to maintain static balance.

• It must be able to support itself without becoming deformed.

• It materials used to construct it must be resistant to both external loads and loads produced by its own weight.

Understand, think, investigate…

1

Intuition and deduction. What are the functions of a tree trunk and the pillars of a bridge?

2 What is the function of the surface of a table and its legs?

1.1 A structure’s design Taking into account the conditions mentioned before we can say a structure is made up of a series of solid elements, joined together and attached to each other, whose function is to support forces, weight and all kinds of loads.

3 Have you ever seen or heard of a structure collapsing because of its own weight? Search online for an example.

When we apply a load to a structure, interior forces are applied to its different components. So, the design of the structure must allow it to firmly maintain its form, as well as maintain its shape.

Avant-garde structures Nowadays, it is popular to build structures that fit well with their environment but are also functional. In other words, their function is still to serve human needs but with a

more avant-garde design. There are lots of newly invented materials which have contributed to the development of these magnificent and impressive structures.

Millennium Bridge. Ourense. Spain.

Single-family residence Plak. Vienna, Austria.

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1.2 Copying nature Human beings have always been natural-born observers of their surroundings and have often copied what nature has provided them with for their own benefit. This curiosity means we have always questioned what we see around us. For example, ‘How can such a tall, thin tree support so many branches and leaves without falling over?’ or ‘Why doesn’t the inside of this cave collapse when there is no central support?’.

The answers to these questions, and our analysis of the natural world, have enabled us to build structures which are constantly improving.

Humans have learnt that the key lies in the correct distribution of the forces and weights exerted on the tree or the walls of the cave, as well as their shape.

Natural structures Some natural structures were formed as a result of the geological evolution of our planet over millions of years. The natural caves in the Cappadocia region of Turkey are an example of this. In these caves, kilometres of galleries and passages were sculpted by water and wind erosion. People have lived in them for thousands of years.

The animal kingdom also provides us with examples of construction.

Animals that have become natural architects and engineers have adapted to their natural surroundings over millions of years. For example, beavers build amazing dams to control the flow of water in a river to protect their lodges (homes). They build these iglooshaped structures using piles of branches and tree trunks. It is interesting that the entrance to their lodge is found at the bottom, partially under the surface of the water, in order to protect them from predators.

Understand, think, investigate…

4 Find other examples of human structures that imitate nature and which are not mentioned in the text. Do you need a clue? Honeycombs, birds’ nests, the anatomical shape of a bird, spider webs and sunflowers, etc.

5

The mirror. Look for the similarities and differences between a dam like the one in the photograph and the ones built by beavers. Are both structures used for the same purpose?

6

Have you heard of caves being used as homes or storage spaces in your region? Maybe you can find somewhere close to where you live. Do some research and tell your class about it.

Natural structures used as dwellings by the inhabitants of Cappadocia.

Dam built by beavers.

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STRUCTURES

1.3 Natural structures as inspiration Many architects and engineers have focused on nature to study and copy its incredible structures. Structures made by termites, like the one shown in the photograph, have been looked at as inspiration to design and build towers. In fact, many architecture students study these structures in biomimicry departments. Biomimicry is a field of science which studies biological or natural structures to solve problems that humans encounter, but that have already been solved by the natural world.

In the city of Harare, Zimbabwe, there is a project which studies the structures made by termites. In this project, an air conditioning system has been created based on how termites naturally oxygenate their termite mounds. This system can save up to 90 % of the energy needed to cool a building. The secret lies in using the natural convection of directed air currents which continually cool the space inside.

A termite mound.

28°C

24°C

Air flowing inside the building in Harare, based on a termite mound.

Understand, think, investigate…

7

Puzzles. The bionic tower is a skyscraper project designed by Spanish architects Eloy Celaya, Rosa Cervera and Javier Pioz at the start of the century. Its structure is based on how fibres are arranged in trees. It is one kilometre high with a minimal base surface area. How do you think it is possible to build this type of architectural giant? Can such tall buildings stay upright? Would it stay standing in a natural disaster such as an earthquake? How many people do you think it could house?

8

Find out more about this and other bionic projects which have a focus on vertical cities for future developments.

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Insects, such as beetles, can extract moisture from the air on misty days, and the structure of a lotus helps it collect moisture on its surface. By looking at these abilities and seeing exactly how these creatures and plants are capable of this, we have been able to copy and apply these techniques to our designs.

Let’s look at a more specific example. Scientists have found a way to use certain materials, such as water-repelling fibres or plastics, to use as a covering for the outer walls of buildings. The specific microscopic structure of these materials means they can be used to supply water directly from the external surfaces of buildings. So when it rains, the water can be directed down to a container for storage. This acts as a possible alternative to natural water supply if there is a drought.

UNIT

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FORCES

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2.1 What are forces?

Forces are pushes or pulls characterised by their value or intensity, or by their orientation. Forces make changes to bodies: they can change their shape (deforming them) or their movement (changing speed or direction).

A force can make an object move in the direction the force is applied to.

Log on to anayaeducacion.es, find the ‘Forces and movement’ simulator and experiment with the forces to better understand how they work.

From the point of view of physics, forces appear when bodies interact with each other and are subjected to an acceleration. For example, when a magnet attracts a screw, or a rock thrown into the air falls back to Earth, or even when we hit a ball or mould a piece of clay. When two objects or bodies interact they acquire speed, which is higher if the body’s mass is smaller.

Therefore, forces can:

• • • •

Move an object at rest.

Stop an object in motion.

Deform an object.

Change the direction a body is moving in.

Forces are represented by arrows with a certain orientation and direction. The length of the arrow gives us an idea of its magnitude.

Spring scale

2.2 How we measure forces

Ring

Spring 20 kg 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 kg

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 kg

There are several instruments that we can measure forces with. The most common is a weighing scale, but in labs a spring scale is also used. In this measuring device a spring extends in proportion to the force applied to it. The graduated scale marks the weight supported by the hook.

Units of measurement Mobile band for marking the weight

Extendable graduated ruler with the spring

Remember the following units because they are important for the calculations that we will do later on:

• Mass is measured in kilograms (kg) in the International System (SI) and is considered one of the seven basic quantities we measure.

• Forces, such as weight are derived from mass, so the units we use Hook

to measure forces are based on mass. The International System uses the newton (N) as the unit for quantifying a force.

A newton is a unit that measures the force exerted by a kilogram of mass subjected to an acceleration of 1 metre per second squared: 1 N = 1 kg · m/s2.

At in anayaeducacion.es you an use a document that will help you to clearly see the difference between mass and weight.

Understand, think, investigate…

9 A block of stone has a mass of 100 kilograms. What

10 Calculate the weight of the stone in the previous

would its weight be? In other words, what is the force with which the Earth attracts it if the attraction of gravity is g = 9.8 m/s2?

exercise on the Moon and on Mars, knowing that the acceleration of gravity on the surface of the Moon is 1.62 m/s2 and on Mars 3.71 m/s2.

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FORCES

2.3 Loads and balance

Dynamic loads

For an object to balance, the sum of all the forces acting on it need to be equal to zero. If this is not the case, as we have seen, the body will be subjected to acceleration in some form. Most objects are meant to be balanced. They are intended to stay still.

A balanced structure is affected by multiple forces. Among these are loads; forces that appear from the weight the object supports. A bridge that supports the weight of the vehicles and people on it, or a table that has a computer resting on it are examples of structures that support loads, maintaining balance.

Loads can be classified as:

• Static loads, also known as dead loads, which do not change over time, such as furniture that is supported on the floor in a room within a building.

Many constructions support static loads and elements. In other words, elements that are not moving. However, many others have to support loads that move.

This adds to the effects of the forces.

a lack of: when something is absent or missing, but is needed.

Centre of gravity

Circle

The weight of snow on a roof or the transit of vehicle traffic on a bridge are both dynamic loads.

• Accidental loads, such as the ones caused by earthquakes, hurricanes and phenomena.

all

kinds

of

high-intensity

meteorological

2.4 The centre of gravity: a key concept for stability

Focus on English

Cube

• Dynamic loads, also known as live loads, which can vary in time.

Triangle

Asymmetrical shape

An object or a structure is stable when the distribution of its mass is balanced as the forces of gravity are acting on it. This definition brings us to a specific concept: the centre of gravity. This is defined as a point in the body of an object in which we imagine all its mass is concentrated. The centre of gravity is a geometric point. Its position, when the body is made of a single material, will depend on its geometry.

For example, the centre of gravity of a symmetrical body will be the geometric centre. In other words, this is the point through which all the diagonal lines that join the opposing vertices cross over each other. In the case of a triangle, the centre of gravity will be located in a point on the central line that determines its height. In a circle, the centre of gravity coincides with the geometric centre.

In asymmetrical shapes (see the bottom-right shape in the diagram on the left) the centre of gravity can be located outside of the body.

This indicates a lack of* stability. Depending on its form and position, the shape could fall while looking for a more stable position.

Understand, think, investigate…

11 Flow chart. Think of a heavy object in motion and draw it in your notebook. How would you represent the force that drives it? What about the force of its own weight? Use arrows to identify each force.

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Think and share with a partner. Remember a time that you were inside a vehicle and the driver made a sharp turn. What happened to you? Did you move? What pushed you? What direction did you move in?

UNIT

2.5 Types of forces and loads

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Deformation

The external forces acting on an object may vary and be distributed differently on its surface, depending on how long they are applied and how they act. These criteria are used to categorise forces and loads:

Distribution and effect of a mound of sand on a platform.

Mound of sand.

Types of forces and loads According to the length of time

fixed

variable

According to how they are applied

concentrated

distributed

Representation of the weight of the sand as it accumulates.

According to their magnitude and length of time, they can be:

• Fixed: their magnitude and direction are always the same, for example, the weight of a building on the ground.

• Variable: their magnitude and direction change continuously. An example of this is the load supported by a bridge when vehicles drive over it.

The reaction of the structure to support the weight of the sand.

According to how they are applied:

• Concentrated: for example, a hammer hitting the head of a nail or how a finger pushes a pin.

• Distributed: for example, snow that has accumulated on a roof, where the load is distributed and its total weight is spread out over the surface.

Look at the example in the picture on the right, which shows a deck supporting a mound of sand. When there is more sand on the mound, the load at the centre of the structure is greater and the load at the ends of the structure is smaller. This causes more deformation at the centre of the deck.

The deformation made to the simple structure if it is made of a material that is not very resistant.

When the weight is heavier, the deformation is greater.

Understand, think, investigate…

13 Give at least one everyday example of a fixed force and one everyday example of distributed loads.

14 Imagine a swimming pool of a consistent depth. The water exerts an even force on the bottom of the pool, as the depth does not vary. Does the same happen on the sides of the swimming pool? What type of load distribution puts pressure on the walls?

15 In the photograph, you can see a dam in a hydroelectric power station. Can you describe what forces are acting and where they are applied? Is the magnitude of the force exerted on the dam greater at the bottom of the reservoir or at the surface? What is the relationship between the water pressure and the forces from the wall of the dam?

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2.6 Stress

Buckling

When a set of external forces acts on an object, the object is deformed by internal forces known as stresses. There are five different types of stresses: tension, compression, bending, torsion and cutting (or shearing).

We will now look at each one in more detail:

• Tension: the stress caused when two forces pull or stretch an object, increasing its length and reducing its cross-section, especially in the middle. This effect is produced when we pull a rope from both ends.

• Compression: this is the stress produced when two forces push down on a piece, which causes its length to decrease and its width to increase. The legs of a chair a subjected to compression when we sit on it.

• Bending: this is when a perpendicular force acts on an object, This is a bending effect that happens to long objects when they are subjected to a heavy load or strong compression force. It is an effect which we need to avoid in construction because it can cause a structure to collapse.

causing it to curve or buckle. This effect is produced when we stand on a board that is only supported at each end and has no support from underneath..

• Torsion: this is when we twist an object and two rotational forces are applied to either end in opposite directions. This effect is produced when we wring a wet cloth.

• Shearing: this is when an object is cut. It occurs when two forces act upon it in opposite directions. We can see this effect when we cut something with scissors, shears or snips.

Types of forces

Tension

Compression

The forces acting on the object make it longer. As a result, the material is stretched.

The forces acting on the object make it shorter. In these circumstances, we say that the object is subject to compression.

Cutting or shearing

Torsion The forces acting on the object twist it; for example, rotating axes.

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Cutting or shearing occurs when the loads acting on the object cut it.

Bending Objects bend or curve. A specific type of bending is lateral bending or buckling.

UNIT

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STRUCTURAL COMPONENTS

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3.1 Structural elements Structures are made up of different elements, and each of them performs a specific function, such as supporting or suspending, or giving a structure its rigidity. As a result, not all of the elements in a structure are subjected to the same stresses.

For example, think of a block of flats in a city. As you already know, the structure must support loads, as well as the building’s own weight, and stand firm against the effects of the different stresses it is subjected to. This includes the wind, seismic movements and traffic vibrations, among others.

But what ultimately supports all of these loads? The total sum of the loads act on the floor and, in most structures, it must be reinforced by foundations. The foundations form an additional, solid and stable base in the ground, which pillars, columns, beams and other structural elements can then be built upon.

Structural elements

Foundations ensure that structural loads are transferred into the ground.

Their design depends not only on the characteristics of the building, but on the nature of the ground as well.

Arches are curved frames in which the forces supported are distributed between the elements that are subjected to compression.

Pillars and columns are vertical elements in a structure. They are mainly subjected to compression.

Beams are horizontal elements in a structure that support the load between two support points. They are mainly subjected to bending.

Braces are steel cables used to provide rigidity to the structure and increase its resistance. Braces are only subjected to tension.

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STRUCTURAL COMPONENTS Did you know that…?

In San Francisco, there are 34 people whose job is to paint the famous Golden Gate Bridge. So that the moisture and the salty air do not corrode the steel which the bridge is made of, the work has to be continuous. Every year 200 000 litres of orange paint, which is designed to conserve the bridge and for the pillars to be seen by sailors in the dense fog.

3.2 Structural failures In order to prevent any potential failure that might occur in a structure, it is important to carry out preventive maintenance work. It is very important to have a good, suitable design for your structure from the beginning, remembering what the function of the structure is as well as its environment. The main causes of structural failure are:

• Material fatigue. Structures are constantly subjected to forces and loads. In many cases, loads are not static but are constantly moving, as in the case of bridges designed for vehicles. As the load moves, vibrations are sent to the structure’s different elements through small and repetitive impacts in every direction. This means that the material the structure is made out of is subjected to more stress and wears down* more quickly.

• Rusting and corrosion. All materials, especially metals, are affected by oxidation processes (rusting), which often lead to corrosion.

This means there is then a loss of mass in the material affected.

Special paints and other anti-corrosion techniques are commonly used to prevent this.

Focus on English wear: damage caused by something being used continuously over a period of time.

• Incorrect structural design. Structures are affected by many

wear down: a phrasal verb used to describe the gradual deterioration of an object or material which makes it weaker.

factors, such as the optimal selection of materials, calculations, location, how the different elements are arranged and how they are assembled, and many other variables. If a mistake is made in the planning and design process, or if important circumstances have not been considered, structural failures will appear. When materials reach a certain level of wear* they can even break and thereby cause the whole structure to collapse.

Understand, think, investigate…

16 Apart from the reasons mentioned above, what other things can cause a structure to fail?

17 Is it true that a round arch (bottom picture) supports more load than a lintel (right)? Explain your answer.

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TYPES OF STRUCTURES

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All structures can be classified into the following groups:

4.1 Mass structures Structure examples

Mass structures have been used since ancient history. They are based on the strength, resistance and permanence of natural structures that can stand the test of time*. They are made up of large, thick stone blocks and the accumulation of materials used to provide support. Some of the clearest examples of mass structures include the Egyptian pyramids, ancient temples, dams and stone bridges, some of which are still standing.

4.2 Framed structures Mass structure.

These structures use resistant elements, such as vertical pillars and columns crossed by horizontal beams to form a framework. Today, they are used to construct the skeletons of buildings and to build scaffolding. A ladder is an example of a simple frame structure.

4.3 Laminated structures Framed structure.

These structures are used to provide cover and protection. They tend to be light and are usually fragile in comparison to other heavier structures. Harder, more resistant laminated structures are usually called exoskeletons.

The most common structures of this type include the outer panels of electrical appliances or the sheets of metal that cover a car.

4.4 Hanging or suspended structures Laminated structure.

This type of structure is based on the use of braces and steel cables to support solid structural elements. Braces and cables are often used in bridge-building projects, which tend to have one or two large towers.

The braces and steel cables that support the bridge are attached to these towers.

4.5 Triangulated structures Focus on English The idiom to stand the test of time means that something remains strong or, in other contexts, remains popular over a long period of time.

Triangles are the only geometrical shape that cannot be deformed.

This means that an object made up of three rigid bars that form a triangle does not change shape when forces are applied to it.

Therefore, triangulation, or making triangles with resistant elements, is the most effective way to make structures more rigid and more difficult to deform.

This type of solution can be seen in buildings and permanent structures, as well as temporary structures such as cranes.

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TYPES OF STRUCTURES Rounded arch

4.6 Vaulted structures Arches and vaults have been used as an architectural solution for thousands of years. However, they are usually only used in special buildings, since they are difficult and expensive to build. The main types of vaulted structures are:

Keystone

Light

Arches There are two very delicate moments when building an arch: fitting the keystone or cornerstone and removing the scaffolding. If the scaffolding is not removed in the correct order, the entire structure could collapse. The simplest and most well-known type of arch is the Roman Arch.

Vaults and domes Domes were the first man-made structure to imitate natural curves.

This type of structure distributes the stress over its sections evenly and is used extensively by architects when they want to emphasise the sense of space and light in a building.

• A vault is a concave body, supported by the walls that surround a space for which it forms a cover or roof. There is a wide variety of vaults: barrel vaults, rib vaults and groin vaults, amongst others.

Understand, think, investigate…

18 Two of the most well-known arch structures are domes and vaults.

Look at their appearance and try to draw their main views in your notebook: front, plan and profile.

• A dome is a type of spherical vault that is made by turning an arch on its symmetry axis. It is used to cover or close a square, octagonal or circular space.

In the past, vaults and domes were used to build churches, cathedrals and palaces. Nowadays, they can also be found in airports, stations and shopping centres.

Vaults and domes

Ribbed vault from the monastery of Nuestra Señora de la Luz, in Lucena del Puerto.

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Dome on the cathedral in Cádiz.

UNIT

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BEAMS

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5.1 Beams Beams are the commercial shapes that are usually made out of steel, aluminium and other materials. The names of each of these beams originate from their cross-section form. These I-, L-, T- and U-shaped beams are elements used to build structures.

A structure must be capable of resisting the different types of stresses they are subjected to. Beams are designed for this purpose. Their particular shapes make it possible to improve resistance, using less material. Distributing the mass away from the beam’s centre of gravity makes it more resistant, whilst using the same amount of material.

The most common types of beams beams Open beams

I, H or double-T beam

T beam

L beam

U beam

Round cross-section

Triangular cross-section

Closed beams

Rectangular cross-section

Square cross-section

Understand, think, investigate…

19 Draw a diagram or a picture of a building’s skeleton

21 Look for a photo of an electricity pylon on the

and try to put all the structural elements in the correct place. Once you have finished your design, answer the following questions.

Internet. You’ll see that it is only made up of bars that form triangles. Can you draw the profile of the type of bar used in the pylon?

Which element would be located in the lowest part?

22 Build open and closed profiles using newspaper,

Which elements are placed horizontally?

Which elements are placed vertically?

20 Look at the double-T beam. Why do you think this shape is used so often in all types of support structures?

cardboard containers, or scrap notebook paper stuck together with tape. Use the same material to make all of your profiles. Do not cut the material; only fold it. Once you have built the beams, test them by putting weight on top. Which one supports the most weight? Why do you think this is so?

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BEAMS

5.2 Trusses Trusses are used in structural engineering. They are made up of simple elements like beams and are usually designed to support roofs or bridges. Trusses are built by making triangular shapes and joining the beams and bars together using brackets. This creates a structure that is resistant to being deformed.

Because the joints or couplings enable the beams to rotate, each one will only work under compression or when subjected to tension.

The main advantage of using trusses is that they are very light in comparison to the weight they can support. As a result, trusses are mainly used to build bridges and as a support element for roofs in large buildings or buildings with large empty spaces inside, for example industrial units, cellars or warehouses.

A truss is built as a single-plane system, using bars and beams.

Successive planes are added to create volume, as shown in the design for an industrial unit below.

Understand, think, investigate…

23 Explain in two or three lines: a) Intuition and deduction. Why are triangles frequently used when building resistant structures?

Once a truss structure has been completed, the roof and walls are put into place in order to finish the building. In this kind of structure, the vertical elements in the truss are subjected to compression.

Water and snow are the main reason why roofs become heavy. For this reason it is important for them to be made to the correct size in order to be able to support much greater loads than usual. This will also depend on the geographical area and climate where the building is to be constructed.

Trusses

A simple truss design used in a bridge.

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The structural design of an industrial unit, using trusses.

UNIT

6

4

MECHANISMS

6.1 Mechanisms

Bench

Different types of movements, or motions, are made depending on how the parts of a mechanism are arranged.

Unlike structures, mechanisms are formed of a set of parts which make a specific movement, transforming a force or using the energy provided by a system to generate it. Normally, mechanisms are secured to a fixed structure. When a structure and mechanisms form an integrated set, it is called a bench.

• Linear motion: this happens when a part moves in a single direction, normally along a straight line.

• Rotary motion: this is when a part moves following a circular path, either clockwise or anti-clockwise.

• Reciprocating motion: when the mechanism moves in a straight line and in both directions.

• Oscillating motion: similar to reciprocating motion, this acts in both directions, but following a circular path or arc.

• Intermittent motion: this happens when the movement of the part in the mechanism starts and stops repeatedly.

Look at the diagram of a locomotive below. The parts that make up the drive system make the different movements described above.

Linear motion

In order to perform their function properly, mechanisms must be fixed, or guided, by a structure that keeps the assembly coordinated. A bench is an integrated assembly of mechanisms and structure.

Rotary motion

Oscillating motion

Reciprocating motion

Understand, think, investigate…

24 Identify the types of motion made in these

b)

mechanisms: a)

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6

MECHANISMS

6.2 Simple machines and mechanisms The first female car mechanic Does the name Benz sound familiar?

Bertha Benz funded the prototype Benz Patent Motorwaggen, patented by Karl Benz in 1886, with her dowry. In August 1888 Bertha drove the prototype some 100km to prove that the tricycle made

by Karl Benz could be driven over long distances. At the time, this was the longest journey that had been made in an automobile. During her journey, Bertha had to do some repairs and make some adjustments to the vehicle.

She made history by becoming the first female driver and mechanic. That same year the first Benz Patent Motorwaggen was sold.

You can find videos online to help you learn more about this landmark in history. Search for the video ‘Bertha Benz: The first driver’.

Every machine is made up of mechanisms and every mechanism, regardless of how complex it is, is made up of basic elements called simple machines or mechanisms.

Inclined planes Moving a heavy object along the floor by pushing or pulling on it is a simple task, but it becomes more complicated when we want to move it to a higher position. The inclined plane makes this task easier by using a surface that joins both heights.

Look at the picture below on the left. Without using the inclined plane, the entire weight (represented by the blue arrow) would have to be supported. However, with the inclined plane, the effort needed is only equivalent to a part of the weight of the load. The smaller the angle of the plane, the lower the force needed to move the object. This advantage has its own disadvantage: the distance we need to push it is larger.

Wedges A wedge is a very simple object with the shape of a triangular prism made from joining two inclined planes. Any force applied perpendicularly to one of its faces will be transferred to the other two. Then the forces transferred to these two faces will also act perpendicularly to them.

When wood is hit with an axe this principle is applied: a vertical force is applied and separates the log horizontally.

Wheels and axles Wheels have a unique characteristic compared to other simple machines: they have a geometric centre. From this point the distance to any point on the edge is always the same. This distance is called the radius of the wheel. The axle, which is a cylindrical part, is joined to the centre of the wheel, forming an integral assembly. So, if the wheel moves, the axle moves too.

Simple mechanisms Inclined plane

Wedge

Wheel

Makes moving a weight upwards easier

Angle A

Weight of the load

The force to overcome is less than the The blade of an axe is shaped like a wedge. weight.

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The rotation of the axle is integrated with the axle of the wheel.

UNIT

4

Screws Screws are the simplest elements for converting a rotary motion into a linear motion going forwards or backwards. This mechanism is more than two thousand years old and is a cylinder with a thread wound around it.

It is like an inclined plane rolled around a cylinder, as you can see in the picture.

Cylinder

Screw Forward movement Inclined plane

Rotation

Screw and nut assemblies Screws are most commonly used in an assembly with a nut, which has the same inner thread.

As the screw turns clockwise, in a nut or in an inner thread, it makes a forward motion. If it rotates anti-clockwise, it makes a backward motion.

This assembly is used a lot in devices to secure parts, in bench vices, or in machines, such as lathes or milling machines. In this example the screw is called a spindle and controls the forward movement of the cutting tool with a high level of precision.

A bench vice uses the screw-nut mechanism.

Understand, think, investigate…

25 Design a small mechanism containing at least two of the three elements simple studied recently.

29 Check the principle of the inclined plane for yourself. Ask your teacher for a spring scale and weigh an object. Write down the result.

26

Considering the invention of the wheel, how do you imagine that the ancient Egyptians transported the large blocks of stone for the pyramids? Explain your own theory in class.

27

Different uses. Do you know another direct application for using a wedge?

Place the dynamometer-object assembly on a wooden table that you keep tilted at a certain angle. Write down and compare the results marked by the spring scale and repeat the experiment while varying the angle. Write down your conclusions.

28 In your technology workshop, count the number

30 Think about how you could build a meter based on

of turns needed to turn a bench vice so that the jaws open one centimetre.

a screw to measure the force of the wind. Apply what you have just studied.

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6

MECHANISMS Levers A lever is a rigid bar whose function is to transfer force and motion.

The lever rests on a bearing point called a fulcrum, and the forces applied cause rotations on the opposite end. The arm supporting the force is called the motor arm, while the part of the lever holding the load or resistance weight is called the resistance arm.

The force applied on one end causes a movement the opposite end.

Learn more about levers in the presentation called “Types of lever”, and about the law of equilibrium by experimenting in the virtual laboratory called “The lever” at anayaeducacion.es.

The force we need to overcome a resistance weight with a lever can be found with the formula below.

F is the driving force (in newtons)

P is the resistance force (in newtons)

FÒd=PÒ D

d is the driving arm (in metres)

D is the resistance arm (in metres)

Depending on the relative position between the force, load and fulcrum, levers can be classified into three types or classes, as you can see in the diagrams below.

Types of levers Lever type 1

Lever type 2

Resistance weight

Fulcrum

The driving arm is longer than the resistance arm, so less force will be needed to lift the load. The fulcrum is between the force and the load. This is a multiplying mechanism.

Resistance weight

Force

Force

d>D

Force

Lever type 3

D>d

Resistance weight

d>D

d

D

d

The fulcrum is located on one end of the lever and the applied force on the other. The load is placed between both of them. This is a multiplying mechanism.

D

This is very similar to type two, but the force and the load change positions, making it a force reducing mechanism.

Model example

Understand, think, investigate…

31 Now solve the same problem from the model example on the right by applying the data to a type two lever. Draw the two levers with force diagrams and identify which one can lift more weight.

32 Now imagine that you change the lengths of the arms. Will you be able to lift the same weight?

Explain your answer.

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What resistance weight will be able to lift a force of 200 N with a type one lever, if the driving and resistance arms measure 3 and 1 metres, respectively?

Solution: Applying the formula for equal rotation of each force, the equation ends up like this: 200 N · 3 m = P · 1 m working out: P=

200 N · 3 m 1m

= 600 N

UNIT

6.3 Rotary mechanisms

4

Pulley systems

Mechanisms that transmit a rotary motion to the axle attached to them are also very common. Let’s have a look at pulleys and gears, which are two of the most commonly used mechanisms.

Pulleys One of the most common elements in rotary mechanisms is the pulley.

A pulley system has a wheel with an axle, called the drive pulley, joined by means of a belt, to another wheel called the steered pulley.

Its purpose is to transfer the rotary motion of the drive pulley to the steered pulley.

Multiplier system.

Depending on the relative diameter of the pulleys, the system will be:

• Multiplier: this is when the diameter of the drive pulley is larger than the steered pulley, causing the latter to rotate at a higher speed.

• Reducer: this is when the diameter of the drive pulley is smaller than the steered pulley, causing the latter to rotate at a lower speed.

Reducer system.

Gears Sprocket systems, or gear systems, are used to transmit and transfer rotary motion along one or several stages of gears. Unlike in pulleys, the wheels of gears must mesh with each other, which is only achieved if the relationship between their diameter and the number of teeth coincide. This number is called the module.

Gear types A

B

There are many types of gears, which are differentiated by the shape and position of the wheels. There are some examples to the right.

6.4 Mechanisms that transform motion Transforming rotary motion into a swaying or reciprocating motion is another common example found in mechanisms and machines. The most commonly used mechanisms to carry out these transformations are cams and connecting rod and crank mechanisms:

Gears for parallel axles (A) and for perpendicular axles (B).

Cam applications

• A cam is a wheel with an oval shape joined to an axle that does not pass through its geometric centre. The cam is in permanent contact with another element, the follower, so that when it rotates it pushes the follower which then makes a linear reciprocating motion.

• Connecting rod and crank mechanisms are used to convert a rotary motion into a reciprocating motion and vice versa. The diagram below shows each step of how it works in a sequence of movements.

Cams are frequently used in cyclic valve control.

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P O H S K R O W Y G O L TECHNO ES R U T C U R T S T H IG E W T H LIG PROJECT Presentation

This project involves using everyday objects to build towers, bridges and other structures.

The main idea is to use things that are long and thin, but which do not necessarily need to be resistant by themselves.

You can make any design, whether it is original or copied from an existing structure. The pictures below show a few examples of structures made by students from other schools.

PROJECT Steps

1 You can use drinking straws, dry spaghetti or rolled-up paper tubes, etc. To make the structure, join them together using tape, electrical tape, hot glue or liquid glue.

2 Before starting, think about which materials will hold the most weight and why.

3 Use a plywood or MDF board as a base.

4 Finally, check your design’s structural efficiency!

Limitations You cannot use more than 30 straws, pieces of spaghetti, noodles or rolls of paper.

Tubes of recycled paper

Drinking straws

Spaghetti and plasticine Drinking straws

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Tubes of recycled paper

S THAT

E CHALLENG

RINT

IMP R I E H T E V LEA UNDERSTAND

1 Copy and complete the sentences about structures below in your notebook.

Structural components 6 Name the different structural elements you can see in the photos below:

– A structure is a massive, complex object, whose ? main function is .... ? is subjected to a .... ?

– Forces appear when a .... motion.

? in the International System – Mass is measured in .... ?

(SI), and units of force are expressed in .... ? of a body – The centre of gravity is defined as a .... ? in which .... is imagined to be concentrated.

2 Identify the type of tensions which the elements numbered in the figures are subjected to.

3

1 4 2

3

5

Can you describe these different terms to a partner? Take turns. If you cannot remember, see if they are in the glossary or if you can find them in an English dictionary.

Concrete Steel Beam Crosspiece Vault Truss Lintel Portico Foundation

4

Answer the following questions: – What is a structure?

– What is a truss?

– What is the main function of a pillar in a structure?

– What is the usual position of a beam in a structure?

– What forces can impact on the braces of a hanging structure? What about on a truss?

5 In order for a structure to remain solid, it has to meet three independent conditions. What are they?

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S THAT

E CHALLENG

RINT

IMP R I E H T E V LEA

13 Test the law of the lever. To do so, use an eraser

UNDERSTAND

and a graduated ruler. Put the eraser on the 10 centimetre mark, which will act as a fulcrum, as you can see in the figure. Get two small bags or containers. Put 25 grams of rice in one and 75 grams of lentils in the other. In fact, you can use any small object. Now check that when you put the lentils at the end nearest the fulcrum and the rice at the furthest end, the lever keeps its balance.

Beams 7 Look at a bicycle like the one in the figure, which uses several profiles. Identify as many of them as possible, and say if they are open or closed, hollow or not. Draw its transverse cross section, as shown in the profile in the example.

Tyre

10 cm

20 cm

Chamber

Cover

8 Different beams and sections are used to form

14 Calculate what force F you would have to apply to lift this wheelbarrow if it was filled with sand whose weight is 750 newtons.

structures in buildings and other constructions.

Look for information on their forms and draw each of them in your notebook. Look for and explain what each of the following types of section are used for: C beam, I beam, H beam.

Mechanisms 9 Identify the type of lever in each of these examples: a)

b)

c) 1m

30 cm

15 Look at the following figure and describe what you see. What mechanism is it?

10 How can we identify a simple mechanism which is able to convert a rotary motion into a forward linear motion?

11 Illustrate with a drawing which forces are generated by a wedge when a force is applied on it.

12 Where would the dark box have to be placed to balance the lever below? What would we have to do so that the lever becomes unbalanced towards the left?

5 kg 30 m

20 m

10 kg

16

10 m 10 m

108

20 m

30 m

What makes you say that? Some authors think that the screw is not a simple machine, but rather that it is based on two others, such as the wheel and the inclined plane. Why do you think they say this?

Remember to select the work material from this unit for your portfolio.

UNIT

17 Look at the cam in the figure. The follower B moves vertically up and down as the cam A turns. The follower rod extends 2 centimetres out of the hole which serves as a guide when point 1 of the cam comes into contact with the wheel on the follower.

How much will the rod extend when point 3 of the cam comes into contact with the wheel?

B

3

Considering the reference of the plane, what forces are acting on it according to what you have studied in this unit? Add the forces to the drawing.

On one side, draw the same inclined plane and the same weight, but this time draw the plane inclined at 30° from the horizontal line. Look at the length of the force in the line of each inclined plane.

Which one is larger? In which of the two cases do you think it will be harder for the weight to go up the ramp? Explain your answer.

19 Look for information or ask people to help you

y

make a list of the most important mechanisms that a combustion motor vehicle has.

3

20 Design a system which can be housed inside a

4

box and which moves a ballerina doll poking out of the top part.

21 In the figure you can see a music cylinder system. cm 12

2

8

cm

1

Look at its mechanism and describe how it works from turning the handle.

18 Draw an inclined plane at 60 degrees (use a protractor to draw on a horizontal line) and place a weight on it which you can represent with a rectangular box. Mark its weight with an arrow.

REFLECT Now we have completed the challenge! Use the following table to evaluate your work. Reflect individually and share your thoughts with your group. Download the table at anayaeducacion.es.

Assessment descriptors

Totally achieved

Quite achieved

Roughly achieved

Developing

By analysing them, I have understood the importance that structures have in buildings and everyday objects.

My pulley train works correctly without going out of the strap or getting stuck.

The triptych structure is stable and holds photos properly.

TEST YOUR SKILLS Check how your skills are improving with the self-assessment tools that you will find at anayaeducacion.es.

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