Question

A ball is vertically downwards with a speed of 6 m/s from a hight of 3.2 m. It strikes a horizontal floor and rebounds back to the same height. The value of corfficient of restitutions (e) is :-

• A. 0.5
• B. 0.6
• C. 0.7
• D. 0.8

Answer 1

The correct option is D 0.8

Velocity just before striking will be $v=\sqrt{u^2+2gh}$ from the $third$ equation of motion.

putting $u=6m/s$ with $g=10m/s^2$ and $h=3.2meter$,

we get $v=10m/s$

velocity $needed$ to reach a height $3.2m$ will be $v_1=\sqrt{2gh}=8m/s$

so the velocity $just$ $after$ $rebounding$ from the ground will be nothing but $v_1$ or 8m/s

so the Coefficient of restitution will be $e=\frac{V_{separation}}{V_{approach}}=\frac{v_1}{v}=0.8$