This Physcast asks us to consider the motion of a block which is falling onto a spring. A 250g block is dropped onto a relaxed vertical spring that has a spring constant k = 2.5 Ncm-1. The block becomes attached to the spring and compresses the spring 12 cm before momentarily stopping. While the spring is being compressed, what work is done on the block by a) the gravitational force and b) the spring force? c) What is the speed of the block just before it hits the spring? (Assume that friction is negligible).