Very basic moment of inertia question
26-5-7
Find the moment of inertia of a plate covering the region bounded by x = -1, x = 1, y = 0 and y= 1 with respect to x axis.
Basic equation
Ix = k integral (x^2 * y)
x^2 * 1
= x^2
Integrate x^2:
1/3x^3
so the answer is k * 1/3x^3
and we would plug 1 into x?
the book answer is 2/3k... any hints? thanks.
Re: Very basic moment of inertia question
I think you have an extra y in the basic equation - it should be 
.
- Hollywood
Re: Very basic moment of inertia question
sorry still not understanding how you got 2/3k in the end
Re: Very basic moment of inertia question
Here's how I did the last step:
![k\int_{-1}^1x^2\,dx =k\left[\frac{x^3}{3} \right]_{-1}^1 =](http://latex.codecogs.com/png.latex?k\int_{-1}^1x^2\,dx =k\left[\frac{x^3}{3} \right]_{-1}^1 = )
^3}{3}-\frac{(-1)^3}{3} \right) = k\left( \frac{1}{3} - \frac{-1}{3} \right)= \frac{2}{3}k.)
- Hollywood
