[問題]求救..一階ODE應用題

[問題]求救..一階ODE應用題

kk66 於 星期二 十月 21, 2008 9:06 am


題目是:
Assume that a shphere of ice melts at a rate proportional
to its surface area, retaining a spherical shape. Interpret
melting as a reduction of volume with respect to time
                                                                                
有2個要求的答案
1.Determine an expression for the volume of ice ar any time t.
                                                                                
2.How long that the volume  will be one-half of the origin, if V(0)=10cm^3.
                                                                                
我只知道表面積A = 4兀r^2

V = 4/3 * 兀r^3 ,  r^3= 3V/4兀
                                                                                
r=(3V/4兀)^1/3 代入 A(表面積)
                                                                                
得到A = 4兀*(3V/4兀) ,
                                                                                
dV/dt= KA
                                                                                
之後就不太會算了
                                                                                
請高手幫一下忙,感謝

kk66
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