Calculate the power of a crane in watts, which lifts a mass of 100 kg to a height of 10 m in 20s.

A body is moved along a closed loop. Is the work done in moving the body necessarily zero? If not, state the condition under which work done over a closed path is always zero.

In an elastic collision of two billiard balls, which of the following quantities remain conserved during the short time of collision of the balls (i.e., when they are in contact).

(a) Kinetic energy.

(b) Total linear momentum? Give reason for your answer in each case.

The average work done by a human heart while it beats once is 0.5 J. Calculate the power used by heart if it beats 72 times in a minute.

Give example of a situation in which an applied force does not result in a change in kinetic energy.