[问答题]
Analyze the motion of a 0li ums/p mc7u1qzr6l* aj78 msimple q;/ht)gua++ tn1rdaa swinging pendulum in terms of energy, (a) ignoring friction, and (b) taking friction into account. Edar)/ u1 qnh +t;at+agxplain why a grandfather clock has to be wound up.
