A bullet of 25 g acquires the velocity of 500 m s−1 after firing from the gun. Find the recoil velocity of a gun having a mass equal to 5 kg.
Mass of bullet, (m1)=25 g=0.025 kg
Velocity of bullet before firing, (u1)=0
Velocity of bullet after firing, (v1)=500 m s−1
Mass of gun, (m1)=5 kg
Velocity of gun before firing, (u2)=0
Velocity of gun after firing = v2
We know that, m1u1+m2u2=m1v1+m2v2
0.025×0+5×0 = 0.025×500 + 5×v2
v2=−12.55=−2.5 m s−1Thus, recoil velocity of gun is equal to 2.5 m s−1. Here, the negative sign shows that gun moves in the opposite direction of that of the bullet.