Question

A ball of mass $400\text{g}$ is dropped to the ground from a height of $30\text{m}$. The ball bounces back multiple times before coming to rest. Which of the following statements is correct?

• A. The work done by air resistance increases if the ball bounces more number of times.
• B. The kinetic energy of the ball increases if the ball bounces more number of times.
• C. The potential energy of the ball increases as the ball bounces.
• D. The work done by gravity increases if the ball bounces more number of times.

Answer 1

The correct option is A The work done by air resistance increases if the ball bounces more number of times.

The potential energy of the ball depends on the height of the ball. It does not depend on the bouncing of the ball.

The kinetic energy of the ball depends on the velocity of the ball.

Gravity is a conservative force. The work done by gravity only depends on the initial and final positions of the ball. Hence, the work done by gravity doesn't depend on the number of times the ball bounces. It only depends on the intial and final heights.

Air resistance is a non-conservative force. Hence, work done by air resistance does increase with the total distance travelled by the ball through air i.e work done by air resistance increases as the bouncing of the ball increases. Option $\left(c\right)$ is correct.