Calculate the recoil speed of a 7kg rifle that shoots a 0.01kg bullet at a speed of 622m/s.

Sure, let's use the principle of conservation of momentum. The total momentum before the bullet is fired is zero (since both the rifle and bullet are initially at rest), and the total momentum after the bullet is fired should also be zero (since there are no external forces).

The momentum of the bullet after it's fired is its mass times its velocity, which is 0.01kg * 622m/s = 6.22 kg*m/s.

Since the total momentum after the bullet is fired should be zero, the momentum of the rifle must be -6.22 kg*m/s (it's negative because we'll say the bullet is moving in the positive direction and the rifle is moving in the opposite direction).

The recoil speed of the rifle (Vr) can be found by rearranging the momentum equation p=mv to v=p/m. So, Vr = -6.22 kg*m/s / 7kg = -0.89 m/s.

The negative sign indicates that the rifle moves in the opposite direction of the bullet, but the speed itself is 0.89 m/s.