A pendulum consists of a 0.500 kg mass on the end of a light rod 50.0 cm
long. It was set swinging so that the greatest angle the rod makes with
the vertical was 30.0º . After 5 hours and 30 minutes it was seen to come
to rest at its lowest position. How much work was done on the
pendulum by the frictional forces? (Answer in J)
(A) – 1.225
(B) – 0.825
(C) + 0.450
(D) – 0.328
答D
这题是一般铅直的单摆？但为何算功，题目还会提到 时间呢？ 麻烦高手解答一下
不知怎么算><
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If the angular velocity is 30 radians per second at t = 0, find the angle
turned through by the wheel between times t = 3 and t = 5 seconds.
Answer in radians.
(A) 260
(B) 320
(C) 380
(D) 500
答D
这题是求角位移是吗？我的想法是，能否直接从角加速度往回积分，这样就可算角加
速
和角位移？
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再麻烦各位大大 给予建议 谢谢~~~^ ^