[题目]在不同高度同时释放两个铅球(不计空气阻力).则在均未落地前.两者( )①在任一时刻具有相同的加速度.位移和速度②落地的时间间隔取决于两铅球释放时的高度③在第1 s内.第2 s内.第3 s内位移之比都为1∶4∶9④两铅球的距离和速度差都越来越大A．只有①②正确 B．只有①②③正确C．只有①③④正确 D．①②③④都正确题目和参考答案——青夏教育精英家教网—

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【题目】在不同高度同时释放两个铅球（不计空气阻力），则在均未落地前，两者（）

①在任一时刻具有相同的加速度、位移和速度

②落地的时间间隔取决于两铅球释放时的高度

③在第1 s内、第2 s内、第3 s内位移之比都为1∶4∶9

④两铅球的距离和速度差都越来越大

A．只有①②正确 B．只有①②③正确

C．只有①③④正确 D．①②③④都正确

【答案】A

【解析】两个铅球都做自由落体运动，所以加速度都等于重力加速度，即加速度相等；由于同时释放，所以运动时间相同；根据公式h=gt2可得发生的位移相等，任意时刻的速度v=gt相等，①正确；两铅球落地的时间间隔为Δt=—，即取决于两铅球下落的高度，②正确；在第1 s内、第2 s内、第3 s内位移之比都为1∶3∶5，③错误；因为是同时释放的，所以两铅球下落过程中相同时间内的位移和速度都相等，故距离差是一个定值，即释放前的高度差，④错误。显然只有选项A正确。

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