(adsbygoogle = window.adsbygoogle || []).push({}); 1. Why is 2(pie)rh multiplied by the dr (change in r) equal to the change in volume?

This is in the case of deriving the moment of inertia of a cylinder; the equation is (change in mass)=2(pie)(radius)(height)(change in radius)(density).

2. Relevant equations

3. The attempt at a solution

I don't quite understand how 2(pie)(radius)(volume)(change in radius) equals change in volume? Is there a proof for this? I can imagine this working mathematically but not conceptually.2(pie)(radius)(height) is just the surface area for each layer, but how does the change in radius come in? I know it has something to do with accounting for the thickness of each hollow cylinder?

All replies are much appreciated. thanks.

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# Homework Help: Conceptual Problem (Integration)

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