- #1

- 50

- 0

I=∫ r

^{2}dm

and dm=dv *density

h=height

r=radius

[tex]\rho[/tex]=density

To get to the correct I=1/2mr

^{2}. you need to make dv=2[tex]\pi[/tex]rh dr

why isn't it dv= dv=[tex]\pi[/tex]r

^{2}h

as in volume=cross-sectional area*height

- Thread starter gboff21
- Start date

- #1

- 50

- 0

I=∫ r

and dm=dv *density

h=height

r=radius

[tex]\rho[/tex]=density

To get to the correct I=1/2mr

why isn't it dv= dv=[tex]\pi[/tex]r

as in volume=cross-sectional area*height

- #2

Delphi51

Homework Helper

- 3,407

- 10

dV = 2πrh*dr

Imagine it "unrolled" into a rectangular solid to see it clearly.

Don't forget the density.

- #3

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Thanks I've been struggling to get my head round that for a while!

- #4

Delphi51

Homework Helper

- 3,407

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Most welcome. Always draw a picture!

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