[问答题]
Analyze the motion of a simple swinging pendu l/ 6wfholpv01lum in terms of energy, (a) ignorin vlp f/l1ho0w6f k0vr 4y/3qjx0ptn9q7u ok-tg friction, and (b) taking friction into account. Explain why a grandfather clock has to be wound 7 qjyxk9 tt4qo/rn-p00v 3ukfup.
