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Please help me solve this Physical Pendulum problem?

Problem 49. It is a question in Fundamentals of Physics Extended version 8th edition

I would be able to solve it if the pivot point was at the end of the stick. But I can't, because there is a part of the stick on both sides of the pivot point.

Please show me how you derived the answer

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1 Answer

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  • Anonymous
    7 years ago
    Favorite Answer

    (a)

    The weight of the stick is solely responsible for its torque.

    Iθ" = mgx sinθ

    Find the moment of inertia of the stick at different pivot points via the parallel axis theorem.

    (mL²/12 + mx²)θ" = mgx sinθ

    (L²/12 + x²)θ" = gx sinθ

    For small oscillations sinθ ≈ θ.

    θ" = [gx / (L²/12 + x²)] θ

    ω² = gx / (L²/12 + x²)

    d(ω²)/dx = [(L²/12 + x²)(g) - (gx)(2x)] / (L²/12 + x²)² = 0

    g(L²/12 - x²) = 0

    x = L/sqrt(12)

    (b)

    ω² = [gL/sqrt(12)] / (L²/12 + L²/12)

    ω² = [g/sqrt(12)] / (L/6)

    (2π/T)² = g sqrt(3) / L

    T = 2π sqrt{L / [g sqrt(3)]}

    Source(s): I am a fan of the Miami Heat and San Antonio Spurs.
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