高中物理试题答案与解析
在光滑的水平面上有甲、乙两辆平板车紧靠在一起,两车质量相同,甲车上有一个质量为m的人,每辆车的质量为人质量的3倍,初始时甲、乙车和人都静止.人以初速度V0从甲车上跳起,落到乙车上后立即向甲车跳去,假设人的速度方向始终水平.整个过程时间很短.![](data:image/png;base64,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)
(i)人相对乙车以多大速度起跳时,才能落到甲车?
(ii)若人能落到甲车上,求乙车对人的最小冲量.
章节:高考物理第六章 动量守恒定律第23讲 动量 动量定理
答案:
(i)向左为正方向,车的质量为M,则M=3m
人跳离甲过程中,人和甲车在水平方向上动量守恒,设人跳离甲车后甲的速度大小为v1,则有 0=Mv1﹣mv0;
从人跳上乙车到人跳离乙车的过程中,人和乙车在水平方向上动量守恒,设人相对于乙车起跳的速度为u,人跳离乙车时乙车的速度大小为v2,则有﹣mv0=m(u﹣v2)﹣Mv2;若人能跳回甲车,有 u﹣v2≥v1;联立解得 u≥.
(ii)从人跳上乙车到人跳离乙车的过程中,对人,由动量定理得
I=m(u﹣v2)﹣(﹣mv0)≥.因此乙车对人最小冲量是
,方向向左.
解析:
(i)分别对人跳离甲的过程和人跳离乙车的过程,运用动量守恒定律列式,即可求解.
(ii)人跳上乙四到跳离乙车的过程,对人,运用动量定理求乙车对人的最小冲量.