Question

A gun fires $20$ bullets/sec each of mass $20\text{gm}$, with a muzzle velocity of $50\text{m/s}$. Find the force required to hold the gun in position.

• A. $20\text{N}$
• B. $50\text{N}$
• C. $8.67\text{N}$
• D. $42.22\text{N}$

Answer 1

The correct option is A $20\text{N}$

Number of bullets fired per second $=n=20$
Total change in momentum per second due to bullets $=\Delta p=nm(v-u)=20\times 20\times {10}^{-3}(50-0)=20\text{kg m/s}$
Force required to hold the gun in position $=\frac{\Delta p}{t}=\frac{20\text{kg m/s}}{1\text{s}}=20\text{N}$