I am defying physics...

N

NRS

Junior Member
Joined
Sep 14, 2009
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62
Or at leats I think I am. I am finding the volume of a solid of rotation. I get 0 as my answer to the volume. I am asuming, that unless I'm working with anti-matter, I'm going to have a volume (half of the solid is below the x axis and half is above) The problem lies here (I have already integrated):


(y^4)/4 - (y^2)/2 solved from -2 to 2

because both of the variables are to a power which is a multiple of two, when I try to solve the definite integral, I get 0.

Is this possible?
 
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Are you sure that your answer is correct . . .
 
Integrals of functions only represent volume (note area = 2-dimensional volume) when the functions are POSITIVE. You need to break the integral into two of them.

Integrate f(x) over [a,b] for which f(x)>=0, and add to that the integral of |f(x)| over [b,c] for which f(x)<0.
 
Actually.... It turns out I made a vary SLIGHT (yeah right) miscalculation, I actually used the wrong radius, It turns out that my original integration wasn't right.
 
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