BEFORE the shot, the cannon is just sitting there with the ball inside.
Their combined momentum is zero.
Momentum is conserved, so their combined momentum has to be
zero AFTER the shot too.
Whatever momentum the ball has in one direction, the cannon
must have the same momentum in the other direction.
Momentum = (mass) x (speed)
Momentum of the ball = (6 kg) x (200 m/s) = 1,200 kg-m/s
Momentum of the cannon =
(2,000 kg) x (speed) = 1,200 kg-m/s
Divide each side by (2,000 kg)
speed = (1,200 kg-m/s) / (2,000 kg)
= 0.6 m/s
That's where the recoil of any gun comes from. The same
momentum as the bullet has, but in the opposite direction.
