Question

# A machine gun fires n bullets per second each of mass m. If the speed of each bullet is v, then the force of recoil is?

Solution

## Since, the momentum of gun and bullet together was zero before firing, so, after firing: momentum of bullets+momentum of gun=0 momentum of the gun=-momentum of the bullets momentum of bullet for each fire=mu since, n bullets are fired per second. Change in momentum of bullet per second=nmu Therefore, change in momentum of gun per second is =-nmu[since direction of gun and bullet are opposite] since, Force=rate of change of momentum Force on gun= -nmu Therefore Force of recoil is=nmu. The force is directed opposite to the direction of the bullets.

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