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There are different types of machines In this topic, you will learn that:
• a wedge or screw can reduce the effort needed to split or enter an object • a wheel and axle is a special lever that turns about a fulcrum.
Many different machines have been developed through the centuries that make less work for us. Ancient Greek mathematician Archimedes (c. 287– 212 bce) developed a screw that carried water to the top of a house. The screw was just a hollow pipe with an inclined plane (a simple machine) wound around the inside. As well as pulleys and levers, other simple machines are ramps, wedges, screws and wheels and axles.
Ramps
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wedge a piece of wood, metal or other substance that tapers to a thin edge and is driven between two objects or parts of an object to secure or separate them
Ramps are the simplest types of inclined planes. A ramp is used to lift heavy objects (the load) up to a higher level. For example, a piano mover might use a ramp to get a piano from the ground onto a truck. Ramps are used to bridge gaps between uneven surfaces. Escalators are moving ramps with steps (Figure 1). A ramp is called a simple machine because it makes moving a load easier. Going up the ramp might take longer than a single step up, but it requires a lot less force from your legs.
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ramp a sloping surface joining two different levels
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Figure 1 An escalator is an example of a ramp.
• inclined planes such as a ramp can provide a mechanical advantage
screw a sharp-pointed metal object with a spiral thread running along its length and a slotted head thread the spiral ridge of a screw
Figure 2 An axe is an example of a wedge.
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Wedges
A wedge is an inclined plane that moves through another object and changes the direction of a downward force to a sideways force. An axe is a wedge. When an axe hits a log, the downward force is changed to a sideways force, which splits the log (Figure 2). Humans discovered the benefits of wedges when they used the jagged edges of rocks to cut animal flesh and skin. It is more than likely that you have used a wedge today: a knife is a wedge and so are your teeth. Each tooth in a zipper is a tiny wedge that fits tightly with the adjacent teeth.
Figure 3 Corkscrews are used to pull the cork out of a bottle.
Screws You might be surprised to know that a screw, like the wedge and the ramp, is also an inclined plane. The indent that spirals around a screw, called the thread, looks almost like a road (a ramp) spiralling up the side of a mountain. Screws penetrate materials such as wood or cork by using the turning effect of a force. The effort needed to turn a screw into an object is much less than that required to hammer the screw into the same object.
Wheels and axles If you have used a circular door handle or travelled in a car, bus or train today, you have used a wheel-and-axle simple machine. A wheel is a type of lever that turns in circles about its centre – the fulcrum or pivot point. An axle usually links the lever and the wheel. For example, when you turn a doorknob, you apply an effort force to the door handle and the
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