Q. A vertical spring with a spring steady of 450-N/m is mounted on the floor. From directly above the spring, which is unstrained, a 0.3 kg block is dropped from rest. It collides with and sticks to the spring, which is compressed by 2.50 cm in bringing the block to a momentary halt. Assuming air resistance is negligible; from what height (in cm) above compressed spring was the block dropped?

Q. A uniform rod of length 0.90-m and mass 19.50 kg is balanced on a sharp edge at 0.660 m from the left end. At the left end hangs a mass of 30kg and the right end hangs an unknown mass so that the whole assembly is in equilibrium. Work out the torque on the center of mass of the rod alone with respect to the pivot point.