A machine gun has a mass of 20 kg . It fires 35 g bullets at the rate of 4bullets per second, with a speed of 400 ms^(-1). What force must be applied to the gun to keep it in position ?

A machine gun has a mass of 20 kg . It fires 35 g bullets at the rate

1.	A machine gun has a mass of 20 kg . It fires 35 g bullets at the rate of 4bullets per second, with a speed of 400 ms^(-1). What force must be applied to the gun to keep it in position ?
Answer» SOLUTION :Mass of GUN, M=20 kg Velocity of bullet, `v=400 ms^(-1)` TIME taken to fire one bullet, `t=1/4` second If F be the average force required to hold the gun in position , then `Fxxt`= change in momentum of gun or `Fxxt = MV[`:.` initial momentum of gun is ZERO ] `:. F=(MV)/t =(20xx0.7)/(1//4)N =56N` Aliter: Number of bullet FIRED per second, n=4 momentum given to the bullets per second = nmv Same momentum per second is gained by the gun . This gives the force acting on the gun and also the force applied to keep the gun in position . So , `F=nmv=4xx0.035xx400N=56N`