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kofmelk
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Homework Statement
Assume that a typical raindrop is spherical. Starting at some time, which we designate as t = 0, the raindrop of radius r sub o falls from rest from a cloud and begins to evaporate.
a) If it is assumed that a raindrop evaporates in such a manner that its shape remains spherical, then it also makes sense to assume that the rate at which the raindrop evaporates - that is, the rate at which it loses mass - is proportional to its surface area. Show that this latter assumption implies that the rate at which the radius r of the raindrop decreases is a constant. Find r(t).
There is a b part but I think I understand how that is done.
Homework Equations
Surface Area of a Sphere is 4*pi*r2
The Attempt at a Solution
-d(m)/dt is proportional to 4*pi*r2
Therefore
dm/dt = -k*4*pi*r2
Where k is a constant to remove the proportionality.
if dr/dt = constant represented by c
then after we integrate that equation we get
r(t) = c1*t + c2
After that I did some really weird math that I don't think is possible. Any ideas?