Question

A small metal pendulum bob of mass 75 g is suspended at rest from a fixed point with a length of thread of negligible mass. Air resistance is negligible. The bob is then displaced to the left.

At time t = 0 the bob is moving horizontally to the right at 0.8 m s^–1. It collides with a small stationary object also of mass 75 g. Both objects then move together with motion that is simple harmonic.

(a) Calculate the speed of the combined masses immediately after the collision. [1]

(b) Show that the collision is inelastic. [3]

(c) Describe the changes in gravitational potential energy of the oscillating system from t = 0 as it oscillates through one cycle of its motion. [1]