Question

We know that If a ball of mass 1 kg is kept at a height 10 m possess potential energy $mgh$ i.e. $(1\times 10\times 10)=100$ J. (Taking Earth surface as reference, where $m$ = mass of object, $g$ = acceleration due to gravity, $h$ = height of object from earth surface.)

what will be the kinetic energy of the ball falling freely from a height of 10 m when it reaches the ground? (take g = 10 $m/s^2$ and neglect air drag)

• A. 100 J
• B. 50 J
• C. 10 J
• D. 0 J

Answer 1

The correct option is A 100 J

Initially, the ball has potential energy which is later converted to kinetic energy.

Potential energy = $1\times 10\times 10=100$ J (at h = 10m)
When the ball reaches the bottom, i.e., h = 0, potential energy will become $1\times 10\times 0=0$ J.

So in absence of air drag, all potential energy will be converted to kinetic energy.

Therefore, kinetic energy when the ball hits the ground will be 100 J.