A boy throws a rubber ball vertically upwards. What type of work, positive or negative, is done:
(a) by the force applied by the boy?
(b) by the gravitational force of earth?

A boy throws a rubber ball vertically upwards.

(a) Work done by the force applied by the boy will be positive as the displacement in the rubber ball is in the direction of the applied force.

(b)Work done by the gravitational force of the earth will be negative as the displacement is in the opposite direction to the gravitational force.