When a ball is lifted to a height of $h$ and then dropped,what is the kinetic energy of the ball just before it touches the ground?

$A$ boy throws a rubber ball vertically upwards. What type of work is done: $(a)$ by the force applied by the boy,and $(b)$ by the gravitational force? Support your answer with reasons.

The velocity of a body moving in a straight line is increased by applying a constant force $F$, for some distance in the direction of the motion. Prove that the increase in the kinetic energy of the body is equal to the work done by the force on the body.

State whether the following statement is true or false:
When a body falls on the ground and stops,the principle of conservation of energy is violated.

In each of the following cases,a force $F$ is acting on an object of mass $m$. The direction of displacement is from west to east,shown by the longer arrow. Observe the diagrams carefully and state whether the work done by the force is negative $(-ve)$,positive $(+ve)$,or zero $(0)$.

Justify,giving proper reasoning,whether the work done in the following case is positive or negative: Work done by gravitational force when a bucket is pulled upwards.