# Question #6a172

Apr 12, 2016

$20000 N$

#### Explanation:

Let the ball be moving in the $x$ direction with a speed of $100 m {s}^{-} 1$.

After hitting the wall, ball rebounds with the same speed. It implies that velocity is reversed but magnitude remains same.
$\therefore$ Change in momentum $\Delta \vec{p} = m a s s \times \left({\vec{v}}_{f} - {\vec{v}}_{i}\right)$
$\Delta | \vec{p} | = 2 \times \left(200\right) = 400 N s$
Time for which force is applied $\frac{1}{50} s$
We know that change of momentum$= \text{Force"xx "time}$
$\implies \Delta \vec{p} = \vec{F} \times t i m e$,
or $\vec{F} = \Delta \vec{p} \times \frac{1}{t i m e}$
$= 400 \times \frac{1}{\frac{1}{50}}$
$= 20000 N$