推 a291110 : 感謝 09/24 08:53
※ 引述《a291110 (none)》之銘言：
: http://i.imgur.com/osuojyd.jpg
題目應該要講是定力F
F dx = m a dx
= m (dv/dt) dx
= m (dv/dx) v dx
= m v dv
F[x_f - x_i] = (1/2) m [v_f^2 - v_i^2]
: http://i.imgur.com/cCCe4E9.jpg
dV / dt = -k V^(2/3)
V^(-2/3)dV = -kt
3V^(1/3) - 3V_0^(1/3) = -k[t - t_0]
3 * 9 - 3 * 10 = -k
3 * 5 - 3 * 10 = -k△T
-15
=> △T = -------------
-3
= 5 (minutes)
: 求解~~微分方程怎麼列都忘光光了
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