如图所示,水平圆盘可绕通过圆心的竖直轴转动,盘上放两个小物体P和Q
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P\u70b9\u7ed5O 1 \u8fd0\u52a8\u4e00\u5468\u7684\u540c\u65f6Q\u70b9\u4e5f\u7ed5O 1 \u8fd0\u52a8\u4e00\u5468\uff0c\u6545T P =T Q\uff0e \u6839\u636ef= 1 T \u53ef\u5f97 f P f Q = T Q T P = 1 1 \u6545D\u9519\u8bef\uff0e\u6839\u636e\u03c9= 2\u03c0 T \u53ef\u5f97\u03c9 P \uff1a\u03c9 Q =T Q \uff1aT P =1\uff1a1\u6545B\u6b63\u786e\uff0e\u6839\u636ev=\u03c9R\u53ef\u5f97v P \uff1av Q =R P \uff1aR Q =1\uff1a2\u6545A\u9519\u8bef\uff0e\u6839\u636ea= v 2 R \u53ef\u5f97 a P a Q = v 2P R P v 2Q R Q = v 2P v 2Q \u00d7 R Q R P = 1 4 \u00d7 2 1 = 1 2 \u6545C\u9519\u8bef\uff0e\u672c\u9898\u7b54\u6848\u4e3aB\uff0e
答案是B。解析中的意思可以这样理解,向心力的公式为F=mw2r,两物体的质量相等所以r越大向心力就越大,这个还是好理解的。当w不断增大时,PQ手里都在不断增大,但是由于他们之间有绳子拉着,所以绳上的拉力和摩擦力共同提供向心力,而r2大于r1所以Q受力大于P受力,因此绳上的力也不断增大,而P所需要的向心力增加的慢些,所以摩擦力就要相应的减小一点,减小到零然后再反向增大。这样说你能明白吗?绛旓細锛1锛夋粦鍧楀湪鍦嗙洏涓婂仛鍦嗗懆杩愬姩鏃讹紝闈欐懇鎿﹀姏鍏呭綋鍚戝績鍔涳紝鏍规嵁鐗涢】绗簩瀹氬緥锛屽彲寰楋細渭mg=m? 2 R浠e叆鏁版嵁瑙e緱锛 ?= 渭g R =5rad/s 鍗冲綋鍦嗙洏鐨勮閫熷害5rad/s鏃讹紝婊戝潡浠庡渾鐩樹笂婊戣惤锛庯紙2锛夋粦鍧楀湪A鐐规椂鐨勯熷害锛歷 A =?R=1m/s浠嶢鍒癇鐨勮繍鍔ㄨ繃绋嬬敱鍔ㄨ兘瀹氱悊锛 mgh-渭mgcos53掳? h...
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