Question 88 of 130

$100$ balls each of mass $m$ moving with speed $v$ simultaneously strike a wall normally and reflected back with same speed, in time $ts$. The total force exerted by the balls on the wall is

A$\dfrac{100mv}{t}$B$\dfrac{200mv}{t}$C$200mvt$D$\dfrac{mv}{100t}$

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Answer: (B) $\dfrac{200mv}{t}$

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Force exerted by each ball is $F=\dfrac{∆p}{∆t}$, here, $p$ is momentum and $t$ is time.
So, for one ball $F=\dfrac{mv-m\left(-v\right)}{t}=\dfrac{2mv}{t}$
Now, total force exerted by the balls on the wall is ${F}_{net}=100\times F=\dfrac{200mv}{t}$.