两个物理问题: 1,如果一个小球静止在水平桌面上,突然重力消失,小球会怎样? 2,汽车正常行驶时,

2025-03-30 16:56:51
推荐回答(4个)
回答1:

  1. 小球保持静止不动。

  2. 车轮与地面有摩擦力,驱动轮产生帮助汽车运动的力,从动轮产生阻碍汽车运动的力。

回答2:

这就是圆锥摆啊。课本上有啊,查查书。受力只有重力和绳的拉力,拉力分解为水平分力和竖直分力,其竖直分力与重力平衡,水平分力提供圆周运动的向心力。

回答3:

1、仍然静止
小球静止在桌面上时只受重力和支持力,支持力是由小球对桌面的压力产生的反作用力。重力突然消失时压力也会消失,所以支持力也突然消失,小球不受力,因此保持静止状态
2、帮助
摩擦力的方向与相对运动的方向或有相对运动趋势的方向相反,汽车正常行驶时轮子相对地面有向后运动的趋势,因此轮子对地摩擦力的方向向前,与汽车运动方向一致,帮助汽车向前运动

回答4:

小球不动,因为桌面的弹力也消失 汽车后轮帮助汽车前进,前轮阻碍汽车前进(不是四驱车)

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