I have seen the derivation for the formula:(adsbygoogle = window.adsbygoogle || []).push({});

h2(pi)rdr used in math textbooks. However, earlier today I had a physics problem where I needed to use the volume of a cylindrical shell of inner radius r and outer radius dr+r and length h. without remembering the formula I tried to derive it starting by determining the area of the base minus the area of the gap:

A=(pi)r^2-(pi)(r+dr)^2

and then multiplying by h

I could not get this in the form h2(pi)rdr starting from where I did.

I understand the derivation given here:

http://www.stewartcalculus.com/data...texts/upfiles/3c3-Volums-CylinShells_Stu .pdf

But I'm just frustrated that I can't understand why the method I tried doesn't reduce to the correct formula. Its simply the area of the base*height!

Why can't that formula be arrived at by my method???

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# Homework Help: Problem Deriving Volume of a Cylindrical shell

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