A metal post is forced straight down into the ground by allowing a heavy object to fall onto it from above. The object has mass $120\text{ kg}$ and the post has mass $40\text{ kg}$ (see diagram). The object strikes the post at speed $8\text{ m s}^{-1}$ and stays in contact with it after the collision.
(a)[2]
Calculate the speed at which the post and object move together immediately after the impact.
(b)[3]
A constant resistive force of magnitude $4800\text{ N}$ acts against the motion. Calculate the distance that the post is driven into the ground.
Worked solution & mark scheme
This 5-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Apply conservation of momentum for the collision: $120\times 8 = 120v + 40v$” …