Question

A metal ball of mass $2kg$ is allowed to fall freely from rest from a height of $5m$ above the ground (Take $g=10m{s}^{-2}$). After the ball hits the ground and comes to rest, mechanical energy is converted to:

• A. heat energy
• B. sound energy
• C. electrical energy
• D. Both A & B

Answer 1

The correct option is D Both A & B

When ball is at rest it will have only P.E that is
$P.E=mgh$

$m=2kg;h=5m$

$P.E=2\times 10\times 5=100J$

This is the total energy as K.E is zero when ball is at maximum height that is when it is at 5m. Hence when ball reaches the ground P.E becomes zero because height is zero. At this point total energy is equal to K.E that is $K.E=100J$.

This $100J$ will convert to heat and sound energy as the ball comes to rest.