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What's the radius of a hollow circle?

Originally posted by: obscenethistle
.25 inch diameter.

.014 inch wall thickness.
Click to expand...

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".
 
Originally posted by: obscenethistle
.25 inch diameter.

.014 inch wall thickness.
Click to expand...

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

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


 
Originally posted by: GodlessAstronomer
Originally posted by: obscenethistle
.25 inch diameter.

.014 inch wall thickness.
Click to expand...

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".
Click to expand...

Yes. *tear*

It is 0.25 inch outer diameter.

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

Correct?
 
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
 
Originally posted by: obscenethistle
Originally posted by: GodlessAstronomer
Originally posted by: obscenethistle
.25 inch diameter.

.014 inch wall thickness.
Click to expand...

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".
Click to expand...

Yes. *tear*

It is 0.25 inch outer diameter.

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

Correct?
Click to expand...

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

Bingo.

/thread

Thank you all.
 
In all seriousness, what would happen if we transferred this to other forums?


Highly Technical?

The Garage?

Politics & News?

Love & Relationships?

All Things Apple?
 
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?
Click to expand...

The circle would take off... duh.
 
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.
Click to expand...

 
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