Physics

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A simple pendulum consists of a light rod of length L = 0.9 m anchored at a fixed point (like the ceiling), and a small mass m = 0.5 kg attached to the free end.  The configuration is moved to an angle θ = 39 degrees from the vertical and released from rest.  Due to the presence of dissipative nonconservative forces (i.e. air resistance and friction at the anchor), 0.17 J of mechanical energy is removed from the system in its swing from θ to the vertical. i.e.  Wnc = -0.17 J. What is the tension (in Newtons) in the light rod at the instant the pendulum is vertical?

  • Physics -

    ΔE=0.17 J,
    h=L(1-cosα)
    PE=KE+ΔE
    mgh=mv²/2 + ΔE
    mv² =2{mgL(1-cosα)- ΔE}
    T= mv²/L + mg = 2{mgL(1-cosα)- ΔE}/L +mg

  • Physics -

    Thank you! Very helpful.

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