Question

A ball bounces to 80% of its original height. What fraction of its mechanical energy is lost in each bounce?

• A. 0.20
• B. 0.60
• C. 0.40
• D. 1

Answer 1

Answer: (A)

0.20

Answer 2

Let the ball is dropped from height h,

Initial potential energy = mgh.

Potential energy after first bounce = mg × 80% of h = 0.80 mgh.

Potential energy lost in each bounce = 0.20 mgh

Fraction of potential energy lost in each bounce

$= \frac { 0.20 \mathrm { mgh } } { \mathrm { mgh } } = 0.20$