Question

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

Answer 1

Given:

Height, h = 5m
Mass, m = 200g (0.2 kg)
$g=9.8m{s}^{-2}$

Solution:
∴ Potential energy = mgh
= 0.2*5*9.8
= 9.8 J

As we know, TE = KE+PE

for instance, at the highest point(h height above the ground)

10 J = 0J+ 10J (in case in the body is released)

for instance, at the lowest point(just before hitting the ground)

10 J = 10J+ 0J
∵ P.E at the highest point= K.E at the lowest point (when it is just about to hit the ground)
∴ K.E energy will be= 9.8 J