Nov 28th, 2012, 21:25 | #1 |
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注册日期: Sep 2009
帖子: 543
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Acceleration (a) is not important here, velocity at the time of contact and the duration of the contact are! The law to use is not Newton's 2nd law of motion, but rather the law of conservation of momentum and conservation of mass-energy. The formulas to use include m1 * v1 + m2 * v2 = constant, f * t = m * v, 0.5 * m * v * v = m * g * h, etc. If elasticity is included (as in all realistic situation), it becomes more complicated. Your pushing of a mass off the table is misleading. f = m * a means that if there is a force, there is acceleration. But when a mass is pushed off the table, the force is not there anymore. So the mass will fall way short of the 1 meter that you suggested. How did you pass 高考? |
老實談太極,認真打太極,追求真太極,嚴防假大空.
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感谢 big bird 此篇文章之用户: |
sunday (Nov 28th, 2012) |