Question

A ball is dropped from a height of 10 m. If the energy of the ball reduces by 40% after striking the ground, how much high can the ball bounce back (in meters)? (Take g = 10 $\frac{m}{s^2}$​)

• A. 6
• B. 4
• C. 3
• D. 9

Answer 1

The correct option is A

6

Let the mass of the object is m kg.

The total energy of the ball at the height of 10 meters = m $\times$ g $\times$ h = 100 m

Since after hitting to the ground, 40% energy of the ball reduces.

Loss of energy of the ball after hitting the ground = 100 $\times$ $\frac{40}{100}$ = 40 m

Energy left on the ball after hitting the ground = 100 m – 40 m = 60 m

Now, 60 m = m $\times$ g $\times$​ $h_1$ ​

$h_1$ ​​= 6 meters