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標題:

Physics Practical 14.1 Q4

發問:

Why statement 3 is correct?? 更新: they attract each other doesn't mean they will fall??

最佳解答:

Note that attraction occurs when (1) Oppositely charged objects are brought together without touching. (2) Charged objects and uncharged object are brought together without touching. The figure in this question shows two spheres repelling each other,so they must be oppositely charged. When the student touches sphere B,sphere B is connected to the earth,i.e. it is earthed.Any net charges on sphere B will be conducted away to the earth.Sphere B becomes neutral then.Therefore sphere A attracts sphere B,and both of them are experienced by the same attractive force,so both spheres will fall 2009-06-17 13:16:24 補充： Initially,both spheres are at a height,say h m from the bottom of the swing. When they attracts,they are experienced by the attractive forces,so they accelerates to the bottom of the swing,that means they fall. 2009-06-17 14:09:03 補充： There must be vertical motion.The simple reason is that the distance from the sphere to the point of suspension should always equal to the length of the stirng,so that the string will not be slackened 2009-06-19 23:33:19 補充： You know that attractions occurs between the two spheres,that means you accept the fact the there are horizontal attractive forces on the spheres,but u think there is along horzontal acceleration but no vertical motion right? 2009-06-19 23:33:36 補充： however,if the two balls just moves horzontally,the distance from the balls to the ceiling would be shorten than the length of the string,the string will be slackened then.Therefore,the balls should also have downward motion,which means the balls fall

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