A machine gun fires a bullet of mass 40 g with a velocity of 1200 m s-1. The man holding it can exert a maximum force on 144 N on the gum. How many bullets can he fire per second at the most?
Answer & explanation
Correct answer: option 3
\(F = \frac{\Delta p}{\Delta t}\)
When the gun applies maximum force :
\(F_{max} = 144 \) N
\(\Rightarrow \Delta t = \frac{\Delta p}{F_{max}} = \frac{m(v-u)}{F_{max}}\)
\(\Rightarrow \frac{0.04(1200-0)}{144} = \frac{1}{3}\) s
∴To achieve the same change in momentum, the minimum time will be 13 s. Any lesser time and the force applied will be greater.
∴ In one second 3 bullets can be fired.