-如图所示,重20牛的物体甲被夹在两块相同的板中间,当两块板各受到50牛的水平压力时甲刚好能匀速下滑,-
------若要将从上方匀速抽出来,所用的拉力为_________牛.
人气:185 ℃ 时间:2019-09-23 04:23:44
解答
匀速下滑时,摩擦力等于重力为20N
匀速抽出来时,摩擦力大小不变但是方向变为向下,重力向下,向下的力一共是 20+20=40N
向上的拉力要与向下的力平衡 相等 拉力为40N
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