Question

A machine gun fires n bullets per second and the mass of each bullet is m. If v is the speed of each bullet then force exerted on machine gun is

• A. $nmV$
• B. $m{V}^{2}g$
• C. $m{V}^{2}n$
• D. $mgV$

Answer 1

The correct option is A $nmV$

Initial velocity of bullet $u=0$

Final velocity of bullet is $v$

Change in momentum of one bullet $\Delta P_1=mv-0=mv$

In one second, number of bullets fired is $n$

So change in momentum of bullets in one second $=\Delta P=n\Delta P_1=mnv$

Force exerted on machine gun by bullets $F=\frac{\Delta P}{\Delta t}$

$⟹F=\frac{mnv}{1}=mnv$