Answer:
A cannon ball of mass 4.0 kg is fired from a stationary 96 kg cannon at 120 m/s. Calculate the velocity of the cannon immediately after firing.
total momentum of cannon and cannon ball before = 0 kg m/s - because neither object is moving
total momentum of cannon and cannon ball after collision = 0 kg m/s - because momentum is conserved
Momentum of cannon ball after firing = 4.0 × 120 = 480 kg m/s.
Momentum of cannon after firing = -480 kg m/s (because it recoils in the opposite direction and 480 - 480 = 0 kg m/s, the total momentum after collision).
Rearrange p = m v to find v:
v = p/m
v = 480 divided by 96
v = 5.0 m/s
Note that the forward velocity of the cannon ball was given a positive value. The negative value for the cannon's velocity shows that it moved in the opposite direction.
