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| 2017/07/04 19:07:28瀏覽49｜回應0｜推薦0 | |
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此文章來自奇摩知識+如有不便請留言告知 [10]Engineer Science Q&A 2發問: A 3kg body is fired vertically upwards from the ground with speed of 200km/h. (a)Find the maximum height it can rise. (b)Its' potential and kinetic energy after 1.5 seconds. 最佳解答: a. Speed, v = 200 km/h= 55.56 m/s By conservation of energy, Loss of K.E. = Gain of P.E. 1/2 mv2 = mgh 1/2 (55.56)2= (10)h Max. height, h = 154 m b. By v = u at v = 55.56 – 10(1.5) Speed at 1.5 s, v = 40.56 m/s Kinetic energy after 1.5 s = 1/2 mv2 = 1/2 (3)(40.56)2 = 2470 J By s = ut 1/2 at2 s = (55.56)(1.5) – 1/2(10)(1.5)2 Distance, s = 72.1 m P.E. at 1.5 s = mgs = 3(10)(72.1) = 2160 J 其他解答: |
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