A gun fires bullets of mass 5 g moving with a velocity $1000 {\text{ms}}^{-1}$. If the average force acting on the gun is 180 N, the number of bullets fired per second is:

Given that, $\text{m}=5\text{g}=5\times {10}^{-3}\text{kg}$                                  

$\text{m}=5\text{g},\text{v}=1000{\text{ms}}^{-1},\text{F}=180\text{N,n}=?\text{u}=0$

We know that:

$\text{F}=\frac{\text{mv}-\text{mu}}{\text{t}}$

$\text{F}=\frac{\text{mv}}{\text{t}}\to$ force acting on each bullet

Force acting on no. of bullets n

$\text{F}=\frac{\text{nmv}}{\text{t}}$

$\Rightarrow \frac{\text{n}}{\text{t}}\text{=}\frac{\text{F}}{\text{mv}}=\frac{180}{5\times {10}^{-3}\times 1000}$

$\therefore \frac{\text{n}}{\text{t}}=\frac{180}{5}=36$