When the wheel on the left begins to turn clockwise;

admin2008-03-12  33

问题 When the wheel on the left begins to turn clockwise;

选项 A、the ball will roll to the left.
B、the ball will roll to the right.
C、the tray will stay level and go up.
D、the tray will stay level and go down.

答案B

解析 通过观察可知,左右两边受力的方向都是向上,根据力矩公式M=FL可计算出两边的受力大小:图中为大小两个滑轮,设力臂分别为L大和L小,则左边受到的力为FL大/L小,右边受到的力为FL小/L小,通过比较,左边受到的力比右边要大,所以球会滚向右边。
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