Cross sectional area

hardernail

Joined Aug 25, 2005
6
Hello,

new to the site and I was wonderin if I could gets some info or feedback. I'm trying to find the cross-sectional area for the object posted. I have found one equation A=.785d^2 while d= large circular diameter - smaller circular diameter not sure if this would be right. I also need an equation for a changing diameter. What the object is suppose to look like is the bottom of a hole with a stopper rod plugging it from the other side. And with the stopper rod opening the cross-sectional area changes. So if I could gets some feedback that would be great. Thx

Craig[attachmentid=896]

pebe

Joined Oct 11, 2004
628
Originally posted by hardernail@Sep 19 2005, 04:12 PM
Hello,

new to the site and I was wonderin if I could gets some info or feedback. I'm trying to find the cross-sectional area for the object posted. I have found one equation A=.785d^2 while d= large circular diameter - smaller circular diameter not sure if this would be right. I also need an equation for a changing diameter. What the object is suppose to look like is the bottom of a hole with a stopper rod plugging it from the other side. And with the stopper rod opening the cross-sectional area changes. So if I could gets some feedback that would be great. Thx

Craig[attachmentid=896]
[post=10458]Quoted post[/post]​
The formula for area of a circle = pi * r * r, where r is the radius of the circle. You have a large black circle and a smaller white one. Subtracting the white from the black area gives the result.

So I think the area =pi * (r1 * r1 - r2 * r2), where r1 is radius of outer circle and r2 is radius of inner circle.