Question

A ball falling freely from a height of $4.9\text{m}$, hits a horizontal surface. If $e=\frac{3}{4}$, then the ball will hit the surface, second time after

• A. $2.0\text{s}$
• B. $1.0\text{s}$
• C. $1.5\text{s}$
• D. $3.0\text{s}$

Answer 1

The correct option is C $1.5\text{s}$

Velocity on hitting the surface
$=\sqrt{2\times 9.8\times 4.9}$
$=9.8\text{m/s}$
Velocity after first bounce
$v=\frac{3}{4}\times 9.8$
Time taken from first bounce to the second bounce $=\frac{2v}{g}$
$=2\times \frac{3}{4}\times 9.8\times \frac{1}{9.8}$
$1.5\text{s}$