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2015-01-20T18:36:36+05:30
Lever
A lever is a bar or board which rests on a turning point. The point on which the lever turns is called the fulcrum. The object to be moved is called the load. The force exerted on the lever is called the effort. 

There are three different types of levers depending on the position of the fulcrum, load and lever.

First class lever : When the fulcrum is between the load and the effort, it is called a first class lever.

For example, think of a common man trying to move a large rock with a pole. Here the rock is the load, the point in the small stone where the lever is resting in the fulcrum and the other end of the lever where force is used as the effort.

Some other examples of first class lever are a pair of scissors and a claw hammer.

Second class lever: When the load is in the middle, fulcrum at one end and effort at the other end, it is called a second class lever.

A wheelbarrow is an example of a second class lever. The weight is the load is the load, the axle of the wheel is the fulcrum and the handles are the effort. A nutcracker is another example of the second class lever.

Third class lever: When the effort is in the middle and load and fulcrum are at the two ends, it is called a third class lever.

A broom, a pair of tongs, a fishing rod and using a cricket bat or a hockey stick to hit a ball are examples of third class lever.

Pulley

A pulley is a small wheel with a groove around its edge. The groove can hold a rope in position.

As the wheel rotates, the rope moves in either direction. It makes lifting of objects, easier. A pulley changes the direction of the lifting force. That means, when you have to lift a heavy object, you pull down the rope and the object lifts up. Pulleys are used for drawing water from wells, hoisting flags and to lift very heavy objects with cranes.

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