Anonymous
Anonymous asked in Science & MathematicsMathematics · 1 month ago

Can someone explain?

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2 Answers

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  • Ash
    Lv 7
    1 month ago

    A) Moment of Inertia of outer box ...

    Iox = a³(b + 30 + 30)/12 = (230³)(280 + 30 + 30)/12 = 230³(85)/3

    Moment of Inertia of hollow area ...

    Iix = (a-30-30)³b/12 = (230-30-30)³(280)/12 = 170³(70)/3

    Moment of inertia of hollow box = Iox - Iix

    =  230³(85)/3 - 170³(70)/3

    = [230³(85) - 170³(70)]/3

    = 230,095,000 mm⁴

    = 2.30 x 10⁸ mm⁴  ← answer to 3 sig fig

    B) Moment of Inertia of outer box ...

    Ioy = a(b + 30 + 30)³/12 = (230)(280 + 30 + 30)³/12 = 115(340)³/6

    Moment of Inertia of hollow area ...

    Iiy = (a-30-30)b³/12 = (230-30-30)(280)³/12 = 85(280)³/6

    Moment of inertia of hollow box = Ioy - Iiy

    = 115(340)³/6 - 85(280)³/6

    = [115(340)³) - 85(280)³]/6

    = 442,340,000 mm⁴

    = 4.42 x 10⁸ mm⁴ ← answer to 3 sig fig

  • ?
    Lv 7
    1 month ago

    Would really like to help, but your print is too tiny to read!

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