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    The question asks to find the moment of inertia around the y axis of the surface bounded by  y = 0 and  y = a - x^2 .

    Have I done it right?

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    (Original post by Plagioclase)
    The question asks to find the moment of inertia around the y axis of the surface bounded by  y = 0 and  y = a - x^2 .

    Have I done it right?

    Looks fine.

    Was puzzled by the "b", but presume that's your standard formula.
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    (Original post by Plagioclase)
    The question asks to find the moment of inertia around the y axis of the surface bounded by  y = 0 and  y = a - x^2 .

    Have I done it right?

    It's usually commonplace to express your answer in terms of the mass of the object, so I'd compute \rho as \dfrac{m}{A}, where m is the mass and A=2\displaystyle\int_0^{\sqrt a} (a-x^2) dx=\dfrac{4}{3}a\sqrt a is the area of the surface. This tidies up the answer slightly.
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    (Original post by Farhan.Hanif93)
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    Thanks. I've not ignored your response to my matrix question by the way, I'll work through that this evening!

    (Original post by ghostwalker)
    Looks fine.

    Was puzzled by the "b", but presume that's your standard formula.
    Thank you.
 
 
 
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