Question

A boy throws a rubber ball vertically upwards. What kind of work is done;

(a) by the force applied by the boy,

(b) by the gravitational force? Support your answer with reason.

Answer 1

When a boy throws the ball in an upward direction with some force, first the ball travels in an upward direction and then falls to the ground with a downward motion.

(a) The force applied by the boy makes the ball fly in the upward direction, as here the direction of force applied and displacement are the same, positive kind of work is done.

(b) By gravitational force, there are 2 possibilities such as,

1. When the motion of the body is upwards, the direction of gravitational force and displacement are in the opposite direction which gives the negative kind of work.
2. When the motion of the body is downwards, there is only gravitational force acting which is the same direction as the motion of the body. this gives positive work done.