Two identical metal spheres are suspended as simple pendulums of equal length. Pendulum P swings in air, while pendulum Q swings completely immersed in a tank of viscous oil. Each pendulum is given the same initial angular amplitude.
(a) Identify which pendulum is lightly damped and which is heavily damped. Give one reason for each identification.
(b) On the same set of qualitative axes, sketch the expected variation of angular amplitude with time for P and for Q over several oscillations.
(c) Which pendulum will retain mechanical energy for a longer duration? Explain your answer in terms of the nature of the resistive force acting on each pendulum.