Work Done
2014-05-13 10:38 pm
A chain of length 10 m and mass 8 kg hanging from the top of a building has a uniform mass density. Find the work done in lifting the lower end of the chain to the same position as the upper end at the top of the building. (g = 9.8 ms^-2 is the acceleration due to gravity.)[Answer: 20g (in J.)]
回答 (2)
2014-05-14 7:55 am
✔ 最佳答案
問題即是將一條鏈對摺。用勢能去考慮此題。上半部的勢能前後不變。下半部可以想成是將一條8/2 = 4 kg 的鏈子向上提升5 m。勢能前後的改變為 4 * 5 g = 20g﹐因此作功也是20g
2014-05-15 6:37 pm
integrate(x=0,5) (10-2x)*(4g/5) dx
= 20g
= 20g
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原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20140513000051KK00062