题干

水平桌面上有一辆小车,张华同学用50N的力水平向右推小车,但小车仍然保持静止状态,请问小车是否受摩擦力?若受,大小是多少?

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解:水平桌面上有一辆小车,张华同学用50N的力水平向右推小车,正因为受到摩擦力的作用,小车才会保持静止状态;此时推力和摩擦力是一对平衡力,大小相等、方向相反.

答:小车受摩擦力的作用,大小是50N.

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