Question

A ball is dropped from a height h. The velocity of the ball when it reaches the ground is $10m{s}^{-1}$. Find h.(Take $g=10m{s}^{-2}$).

Answer 1

Step 1: Given data.

The velocity of the ball when it reaches the ground v$=10m{s}^{-2}$.

Acceleration due to gravity $g=10m{s}^{-2}$.

Step 2: To find height h.

A ball under free fall obeys the law of conservation of energy.

According to the Law of conservation of energy of a freely falling body, the potential energy at the time of drop and the kinetic energy just before reaching ground will be equal.

$mgh=\frac{1}{2}m{v}^2$

$h=\frac{v^2}{2g}$

$h=\frac{{10}^2}{2\times 10}$

$h=5m$.

Hence, the height h is $5m$.