A ball of mass 0.3 kg is moving vertically downwards with speed \(8 \mathrm {~m} \mathrm {~s} ^ { - 1 }\) when it hits the floor which is smooth and horizontal. It rebounds vertically from the floor with speed \(6 \mathrm {~m} \mathrm {~s} ^ { - 1 }\). Find the magnitude of the impulse exerted by the floor on the ball.
(3)
A railway truck \(A\) of mass 1800 kg is moving along a straight horizontal track with speed \(4 \mathrm {~m} \mathrm {~s} ^ { - 1 }\). It collides directly with a stationary truck \(B\) of mass 1200 kg on the same track. In the collision, \(A\) and \(B\) are coupled and move off together.
Find the speed of the trucks immediately after the collision.
(3)
After the collision, the trucks experience a constant resistive force of magnitude \(R\) newtons. They come to rest 8 s after the collision.