Lever
Levers are a simple machine, they are useful to us because they give us an advantage. A lever is a bar that rests on a fulcrum so that when you exert a downwards or upwards force on one end of the bar, the other end moves in the opposite direction.
As levers give us an mechanical advantage (sometimes disadvantage, but useful) they are used to move large amounts of mass with much less force than is usually required. You can make the work easier by simple extending the bar. There are many uses for levers but some are listed below: - Your elbow (Class 3)
- Scissors (Class 1) - See saws (Class 1) - Nutcracker (Class 3) |
There are three types of levers that are based upon where the load (heavy object) and effort are located in relation to where fulcrum is. The levers are:
Class 1 Lever (Mechanical Advantage) Class 2 Lever (Mechanical Advantage) Class 3 Lever (Mechanical Disadvantage) You can find pictures below |
Wheel and Axle
One way to understand what the wheel and axle is, you can imagine it being in fact two machines, they are the Axle, and Wheel. The wheel spinning by itself has no direction, i.e it goes wherever it wants. The axle by itself is just a stick that could be used as a lever. However when you put the two together you get a very useful simple machine.
As mentioned above the wheel and axle are very useful, some examples are:
Turbines Steamrollers Motorbikes Cars |
As mentioned previously this simple machine is in two parts, the wheel, and axle. The diameter of the axle is smaller than the wheel. The load is normally placed onto the axle, and the effort is done through the wheel. Since the wheel is larger than the axle, say ten times larger. Then the effort you applied on the wheel, would become ten times as great in the axle, their by increasing the force. However the reverse of this can increase the speed at which the wheel turns.
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Screw
Screws have been classified as a simple machine, which is in a way misleading. They can be thought of as a complex machine as they use a inclined plane that has been wrapped around a cylinder.
They are used in:
Drill Bits Cork Screws Certain Digger heads Jar Lids |
Screws are useful as they can transform a turning effort into a up and down one. They are widely used in sticking two materials together, because they are very hard to come loose.
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Wedge
Just like a screw a wedge can be considered as a complex machine as it made of two inclined planes. Wedges can be both used as something to jam something open (door), or to split something apart (axe).
Some uses for wedges include:
Door Stoppers Axes Jackhammers Knifes |
How well a wedge performs as something to split a material mainly depends on what materials each is made of. However if you wedge is longer and thinner, then they are easier to drive into the material you are splitting but you may find it harder to split. The opposite is in effect for thick and short wedges, i.e, it is harder to drive in, but one inside it is easier to split the material.
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Pulley
Pulleys are a very versatile simple machine. They can be used to pull up very heavy items. They are made of a wheel and axle with a rope or another rope like material going through it. When you pull on one end of the rope the other end rises and lifts the heavy object on the other end.
Pulleys are used in:
Cranes Fishing Rods Weight Lifting Machines |
The pulley reduces the weight you have to pull up the rope, but you have to pull a longer distance, thereby not breaking the Law of Conservation of Energy. The more pulleys you add, the lighter it gets but the more you have to pull.
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Inclined Plane
A Inclined plane is nothing more than a flat surface the is sloping. A inclined plane works when it connects a lower height to a higher height. When you push an heavy object up a ramp (inclined plane), you are using less force than if you were pushing the objects straight up.
Inclined Planes are used in:
Ramps Wedges Bridges Screws |
The longer and less steep a ramp is then the easier it is to push an object up, but you have longer to push. On the reverse side, the more steep and short it is, the harder it is to push the object, but less time you push it.
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