作者Honor1984 (希望愿望成真)
看板Physics
标题Re: [题目] 普物一题
时间Sun Nov 2 00:15:16 2008
※ 引述《chenkaihsu (Shrek)》之铭言：
: [领域] 大一普物 (题目相关领域)
: [来源] 课本 (课本习题、考古题、参考书...)
: [题目] An object of mass m is traveling on a horizontal surface. There is a
: coefficient of kinetic friction 摩差系数b between the object and the surface. The
: object has speed v when it reaches x=0 and encounters a spring. The object
: compresses the spring, stops, and then recoils and travels in the opposite
: direction. When the object reaches x=0 on its return trip, it stops.
: Find k in terms of b mg v
: [瓶颈] (写写自己的想法，方便大家为你解答)
: 我列式出来是 1/2*mv^2=bmgd+1/2*kd^2(设d为压缩距离)但我解不出来....有2ㄍ未知数
1/2*mv^2=bmgd+1/2*kd^2
1/2*kd^2 - bmgd = 0
=> d = 2bmg/k
=> k = 2bmg/d --------(1)
1/2*mv^2=2bmgd
=> d = 1/4 * v^2/bg代入(1)
=> k = 8 b^2g^2m/v^2
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※ 发信站: 批踢踢实业坊(ptt.cc)
◆ From: 122.124.102.144
※ 编辑: Honor1984 来自: 122.124.102.144 (11/02 00:17)
1F：推 chenkaihsu:还是不太懂,,,,,可以说明一下吗?? 11/02 11:43
2F：→ Dirac5566:他第二条是弹回来的能量消耗 11/02 13:50
3F：推 su3g45j:你不懂？代表撞一次所需的能量 11/02 19:21