Name the form of energy which a body may possess even when it is not in motion. 

Give any two effects of a force on a non-rigid body.

Where is the center of gravity of a uniform ring situated? 

The position of the center of gravity of a body remains unchanged even when the body is deformed.’ State whether the statement is true or false.

5.

A force is applied on a body of mass 20 kg moving with a velocity of 40 m/s. The body attains a velocity of 50 m/s in 2 seconds. Calculate the work done by the body.

With reference to their direction of action, how does a centripetal force differ from a centrifugal force. 

One end of a spring is kept fixed while the other end is stretched by a force as shown in the diagram.

i) Copy the diagram and mark on it the direction of the restoring force. (figure required)

ii) Name one instrument which works on the above principle.

A girl of mass 35 kg climbs up from the first floor of a building at a height 4 m above the ground to the third floor at a height 12 m above the ground. What will be the increase in her gravitational potential energy?

State the principle of conservation of energy. 

A type of single pulley is very often used as a machine even though it does not give any gain in mechanical advantage.

i) Name the type of pulley used.

ii) For what purpose is such a pulley used?