How to Calculate the Centroid of a Half Circle?

[JJones_86]

Homework Statement

Calculate the location of the centroid (See PDF)

----------------------------------------
I am stuck on how to find the centroid of a half circle, item #5. I don't how to find the distance of that centroid on the x-axis. Any help is appreciated. Thanks!

 

[JJones_86]

No one knows?

 

[cristo]

Firstly, you should learn some patience: the homework helpers here give up their time voluntarily, and so you cannot demand that they answer your question within a couple of hours of posting, especially if you do not conform to the homework rules. Where is your work? What have you tried for the problem? How do you calculate a centroid, in general?

 

[JJones_86]

Firstly, you should learn some patience: the homework helpers here give up their time voluntarily, and so you cannot demand that they answer your question within a couple of hours of posting, especially if you do not conform to the homework rules. Where is your work? What have you tried for the problem? How do you calculate a centroid, in general?

I didn't demand nothing, I simply asked a question and was trying to bump the thread because my .pdf was pending approval for awhile. Second, I didn't ask how to calculate a general centroid. Finally, I asked how to calculate the centroid of a half circle. There was no work to be shown because I had no idea how to calculate the centroid of a half circle. I didn't try anything on this problem.

 

[mgb_phys]

I was waiting for the attachment to approve to see what work you had already done.
Presumably you have done calculus to be asked this question?

You should look up a semicircular lamina, there is a difference between the CofG of a semicircle (ie a wire forming half a rim) and a half a disc.

You can find an explanation here:
http://books.google.com/books?id=4w...&hl=en&sa=X&oi=book_result&resnum=6&ct=result

 

[JJones_86]

I was waiting for the attachment to approve to see what work you had already done.
Presumably you have done calculus to be asked this question?

You should look up a semicircular lamina, there is a difference between the CofG of a semicircle (ie a wire forming half a rim) and a half a disc.

You can find an explanation here:
http://books.google.com/books?id=4w...&hl=en&sa=X&oi=book_result&resnum=6&ct=result

Thank you for answering my question in a kind manner unlike some other people... Anyways I figured it out, but again, thank you!

 

[Perillux]

Would you mind posting your solution?

 

[JJones_86]

Sure, the equation i used is 4*R/3pi, in my case it was (4*4in)/(3*Pi) which gives me 1.69765in, which is the distance from the center towards x-direction.

 

[mgb_phys]

Looking at your attachment this is an engineering question about the CofG of a complex shape that involves a semicircle. So in this case it's probably perfectly reasoanble to just lookup the equation and use it.
If this had been a maths/calculus question asking you to prove the CofG of a semicircle then us telling you that the answer is 4*R/3pi does no good - that was cristo's point.

Attachments have to be individually checked / approved by one of the site mentors, this takes time but is need to stop people just posting junk/porn images. There was a big server move this weekend and the mentors are busy fixing the problems that that caused.