如图,把A、B小球由图中上位置同时由静止释放（绳开始时拉直）,下列正确的是( )A.绳OA对A球做正功B.绳AB对B球不做功C.绳AB对A球做负功D.绳AB对B球做正功

如图,把A、B小球由图中上位置同时由静止释放（绳开始时拉直）,下列正确的是( )A.绳OA对A球做正功B.绳AB对B球不做功C.绳AB对A球做负功D.绳AB对B球做正功
如图,把A、B小球由图中上位置同时由静止释放（绳开始时拉直）
,下列正确的是( )
A.绳OA对A球做正功
B.绳AB对B球不做功
C.绳AB对A球做负功
D.绳AB对B球做正功

如图,把A、B小球由图中上位置同时由静止释放（绳开始时拉直）,下列正确的是( )A.绳OA对A球做正功B.绳AB对B球不做功C.绳AB对A球做负功D.绳AB对B球做正功
答案是D,因为球A,B角速度相等,而半径0B大于OA,故B球速度大于A球,即B球动能大于A球.但是A,B下降高度时刻相等,所以B多出的动能由绳AB做正功提供,选D.
码字挺累的,

∵力的方向斜向上
∴那个力的分力与位移方向相反
∴绳OA对A做负功
但∵A和B同时被释放
∴都做自由落体运动
∴状态与原来的状态一样
∴绳AB不会对B做功

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B
力与速度垂直，所以始终不做功。

A,B两球在下降过程中重力势能的减少量相同，可以考虑为重力势能转化为动能，在某一点的动能之和是一定的，如果A,B同高则动能相同互不影响，图中明显B的动能大于A的动能，有A通过绳AB对B做功