给你出道题：用解微分方程的方法求逃离速度

送交者: Amargi 于 2011-01-28, 20:02:52:

A rocket m is launched from the earth M vertically away with initial velocity V

DV/Dt=-gmM/X^2

i.e

d2X/dt2=-gmM/X^2

Please give teh analytic form of X as a function of
(t) and seem what is the minimum V that can ensure x goes to inifity.

(Please do not use the law of conservation of energy,
which make the problem too easy)

A more realistic question about rocket is that - steven (352 bytes) 2011-01-29, 02:54:50 (542421)
constant times ln(x)？ (无内容) - SB (0 bytes) 2011-01-28, 20:20:04 (542311)
这种数学题有什么好做的。 (无内容) - JFF (0 bytes) 2011-01-28, 20:10:12 (542302)
- SB。你给我做做 (无内容) - Amargi (0 bytes) 2011-01-28, 20:12:56 (542304)
  - SB。我为什么要去做解微分方程的数学题？ - JFF (204 bytes) 2011-01-28, 20:17:59 (542308)
    - SB。那问你一个不需要数学的题 - Amargi (93 bytes) 2011-01-28, 20:35:43 (542322)
      - 嘛叫逃离速度？我的物理课中从没学过第几宇宙速度这类问题。 - JFF (216 bytes) 2011-01-28, 20:43:06 (542324)
        
        你生活中有“逃离速度”这样的物理问题吗？ (无内容) - JFF (0 bytes) 2011-01-28, 21:23:59 (542343)