What's the radius of a hollow circle?

Oct 27, 2007
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Originally posted by: obscenethistle
.25 inch diameter.

.014 inch wall thickness.

0.25" inner or outer diameter?

Radius is half the diameter.

If 0.25" inner diameter, then the inner radius is 0.125", outer radius is 0.139". If 0.25" outer diameter, outer radius is 0.125", inner radius is 0.111".
 

RichardE

Banned
Dec 31, 2005
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Originally posted by: obscenethistle
.25 inch diameter.

.014 inch wall thickness.

Is there material between the center and wall or is it truly hollow?

Being hollow doesn't matter. :p Just treat it like a regular circle/sphere/cylinder.


 

oiprocs

Diamond Member
Jun 20, 2001
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Originally posted by: GodlessAstronomer
Originally posted by: obscenethistle
.25 inch diameter.

.014 inch wall thickness.

0.25" inner or outer diameter?

Radius is half the diameter.

If 0.25" inner diameter, then the inner radius is 0.125", outer radius is 0.139". If 0.25" outer diameter, outer radius is 0.125", inner radius is 0.111".

Yes. *tear*

It is 0.25 inch outer diameter.

So when I calculate the area, it is going to be pi*(.014)*2.

Correct?
 
Oct 27, 2007
17,009
5
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Nope. You want the surface area? Like if this is a cross section of a pipe, you want the area of the solid bit? That would be
A = pi(0.125)^2 - pi(0.111)^2
= pi(0.125^2 - 0.111^2)

Or do you want the area of the open bit, which is just A = pi * (0.125-0.014)^2 = pi * (0.111)^2
 

Fayd

Diamond Member
Jun 28, 2001
7,970
2
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www.manwhoring.com
Originally posted by: obscenethistle
Originally posted by: GodlessAstronomer
Originally posted by: obscenethistle
.25 inch diameter.

.014 inch wall thickness.

0.25" inner or outer diameter?

Radius is half the diameter.

If 0.25" inner diameter, then the inner radius is 0.125", outer radius is 0.139". If 0.25" outer diameter, outer radius is 0.125", inner radius is 0.111".

Yes. *tear*

It is 0.25 inch outer diameter.

So when I calculate the area, it is going to be pi*(.014)*2.

Correct?

if you're working with wall thickness, then the problem is probably asking for the interior area. so it'd be pi*.111^2
 

oiprocs

Diamond Member
Jun 20, 2001
3,780
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Originally posted by: GodlessAstronomer
Nope. You want the surface area? Like if this is a cross section of a pipe, you want the area of the solid bit? That would be
A = pi(0.125)^2 - pi(0.111)^2
= pi(0.125^2 - 0.111^2)

Or do you want the area of the open bit, which is just A = pi * (0.125-0.014)^2 = pi * (0.111)^2

Bingo.

/thread

Thank you all.
 

shortylickens

No Lifer
Jul 15, 2003
80,287
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In all seriousness, what would happen if we transferred this to other forums?


Highly Technical?

The Garage?

Politics & News?

Love & Relationships?

All Things Apple?
 

Homerboy

Lifer
Mar 1, 2000
30,890
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Originally posted by: shortylickens
In all seriousness, what would happen if we transferred this to other forums?


Highly Technical?

The Garage?

Politics & News?

Love & Relationships?

All Things Apple?

The circle would take off... duh.
 

RichardE

Banned
Dec 31, 2005
10,246
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Originally posted by: shortylickens
In all seriousness, what would happen if we transferred this to other forums?


Highly Technical? You would be more confused

The Garage? Wrong Forum

Politics & News? They would blame Bush, the Jews and Mexicans at the same time for making the math too difficult and hail Obama as the change needed and look forward to understanding math somehow because he got elected... no one knows how or why you would now suddenly understand math, but it would happen

Love & Relationships? Dirty jokes about the circumference not being big enough for my member than /lock

All Things Apple? They wouldn't get it.