Question

A ball of mass $200$ gram falls from a height of $5$ metre? What is its kinetic energy when it just reaches the ground? $(g=9.8{ms}^{-2})$

Answer 1

The sum of kinetic energy and potential energy is always constant.

When ball is at the height of 5 m, it has only potential energy which is = mgh

=0.2×9.8×5 = 9.8 J

(Mass in kg =0.2 kg , g=9.8)

When it reaches on ground,all its P.E converts in K.E

So,K.E when ball reaches to ground = 9.8 J