Question

A gun of mass 10 kg fires 4 bullets per second. The mass of each bullet is 20 g and the velocity of the bullet when it leaves the gun is 300 ms. The force required to hold the gun when firing is

• A. 6 N
• B. 8 N
• C. 24 N
• D. 240 N

Answer 1

Answer: (C)

24 N

Answer 2

Momentum of one bullet, p = mv = 20 ? 10$^{-3}$ ? 300 = 6 kg m s$^{-1}$ N = number of bullet per sec = 4 $? \frac{dp}{dt}=$ change of momentum per sec or force $\quad$ $\quad$ $\quad$= N(p - 0) = 4 ? 6 = 24 N