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 $300m{s}^{-1}$ the force required to hold the gun while firing is:

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

Answer 1

The correct option is C $24N$

Rate of change of momentum of the bullet in the forward direction
= Force required to hold the gun= $\frac{\Delta p}{t}$

$P_{bullets}=20\times {10}^{-3}\times 300=6$

so four bullet fire in 1 sec is 4, therefore $P_{bullet}=4\times 6=24$

as we have to find the force to hold the gun i.e, $P_{gun}=0$ as it is in steady state

so Net change in momentum i.e, $\Delta P=0-24=-24$ -ve sign means it will recoil in a backward direction.

$F=\frac{\Delta P}{t}=\frac{24}{1}=24N$