问题:
如图所示,用滑轮组把重为200N的货物提到9m高的楼上,所用拉力为80N;则总功和滑轮组的机械效率分别是
A.1800J,83.3%
B.2160J,83.3%
C.1400J,80%
D.1800J,80%
如图所示,用滑轮组把重为200N的货物提到9m高的楼上,所用拉力为80N;则总功和滑轮组的机械效率分别是
A.1800J,83.3%
B.2160J,83.3%
C.1400J,80%
D.1800J,80%
A.1800J,83.3%
B.2160J,83.3%
C.1400J,80%
D.1800J,80%
参考答案: