Question

A ball of mass 200g strikes a rigid wall normally with a speed of 25m/s bounces back with the same speed. Time of contact of ball with wall is 1sec. Calculate i) the change in momentum ii) force exerted by ball on the wall.

Answer 1

Here, $m=200g=200\times {10}^{-3}kg$
Initial velocity, $u=25m/s$
Final velocity, $v=25m/s$
Time, $t=1s$

i) Impulse, $I=$change in linear momentum $=m(v-(-u\left)\right)$

$$\begin{gathered} =200\times {10}^{-3}\times 25-(-25) \\ =10N-s \end{gathered}$$

ii) Force exerted by ball on the wall $=\frac{Impulse}{t}$

$=\frac{10}{1}=10N$