一质量为m的物体在保守力作用下,做圆周运动,运动一圈,则保守力所做的功一定为零。
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质点系中的一对内力不能改变质点系的总动能。
A. 对
B. 错
An _________ meeting was held to discuss the problem.
A. promising
B. extraordinary
C. universal
A seasonal wind can _______ a large amount of rainfall.
A. bring in
B. bring up
C. bring for
It is the _________ American television series.
A. rated
B. top-rated
C. rate