Wikipedia:Reference desk/Archives/Mathematics/2018 April 26

= April 26 =

Different ways of calculating center of mass
All the methods should give the same result, but I'm getting different answers. Also, I don't know how to use the line integral to finish the problem. Imagine Reason (talk) 00:27, 26 April 2018 (UTC)
 * Why would you use a line integral to calculate something for a solid?—Jasper Deng (talk) 04:06, 26 April 2018 (UTC)


 * This is a surface, so it should be possible. Anyway the other methods don't agree either. 134.74.251.209 (talk) 13:40, 26 April 2018 (UTC)


 * Method 2 is correct. As for method 1, the $$\overline x$$ being an abscissa of a center of mass does not mean the masses below and above $$\overline x$$ are equal. If it did, the center of mass would not exist for any configuration of two different point masses! --CiaPan (talk) 15:15, 26 April 2018 (UTC)
 * I see your point. So how would I check my answer? As for the line integral, I was trying to apply Pappus's_centroid_theorem. 161.185.160.75 (talk) 16:46, 26 April 2018 (UTC)
 * I'll post it shortly, but the answer I get for the surface area using Pappus's theorem is 0.09141, which is supposedly the correct answer, even though the normal method, integrate 2*pi*y over x from 0 to 0.2, results in a surface area of 0.08378. 161.185.161.23 (talk) 20:42, 26 April 2018 (UTC)
 * You might be interested in reading on the difference between mean and median. The center of mass is based on the mean, whereas a line dividing the object into two equal masses corresponds to the median. -- Meni Rosenfeld (talk) 22:44, 26 April 2018 (UTC)