Describe three orders of levers giving an example of each. Draw neat diagrams showing the positions of fulcrum, load and effort in each kind of lever.

1. Lever of Class I : The lever in which the fulcrum is in between the load and the effort are called lever of class I. Generally, the effort arm of lever of class I is longer than the load arm, therefore, the mechanical advantage of a class I lever is greater than 1. However, if the effort arm is equal to the load arm, the mechanical advantage is equal to 1. But if the effort arm is shorter than the load arm, its mechanical advantage is less than 1. Thus, the mechanical advantage of a lever of class I can be greater than 1, equal to 1 or less than 1. Example : see-saw.

2. Lever of Class II : The lever in which the load is in between the fulcrum and the effort are called lever of class II. In class II lever, the fulcrum is at one end and the load is closer to the fulcrum. Thus, the effort arm is always longer than the load arm. Hence, the mechanical advantage of a class II lever is always more than 1. Example : nut cracker.

3. Lever of Class III : The lever in which the effort is in between the fulcrum and the load are called lever of class III. In class III lever, the fulcrum is at one end and the effort is close to the fulcrum, thus the effort arm is always shorter than the load arm. Hence, the mechanical advantage of a class III lever is always less than 1. Example : knife.