When a ball is thrown vertically upwards,its velocity goes on decreasing. What happens to its potential energy as its velocity becomes zero?

State the law of conservation of energy.

Four persons jointly lift a $250 \,kg$ box to a height of $1 \,m$ and hold it.
$(a)$ Calculate the work done by the persons in lifting the box.
$(b)$ How much work do they do just holding it?
$(c)$ Why do they get tired while holding it? $(g = 10 \,m/s^2)$

$A$ person is holding a bucket by applying a vertical force of $10 \,N$. He moves a horizontal distance of $5 \,m$ and then climbs up a vertical distance of $10 \,m$. Calculate the total work done by him. (in $J$)

$(a)$ Define kinetic energy.
$(b)$ The masses of a scooter and a bike are in the ratio of $2:3$,but they are moving with the same speed of $108 \, km/h$. Compute the ratio of their kinetic energy.

$A$ light and a heavy body have the same momentum. Which one will have greater kinetic energy?