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Homework Help: Torque Calculation & Error Question

  1. Dec 4, 2011 #1
    1. The problem statement, all variables and given/known data

    This is a problem from an experiment wherein one must find the point of equilibrium for a horizontally-projected rod that hinges from it's left endpoint. I have already performed the experiment, and now have to calculate the error by comparing the torques pulling down on the rod to the torque pulling up via a string looped around a pulley to a hanging mass. This must be done in two specific scenarios.


    Mass, length of rod: .1131kg, .577m
    W1 weight attached to rod, dist. from hinge: .1177kg, .38m
    W2 weight attached to rod, dist. from hinge: .2502kg, .529m
    W3 weight attached to string: .2502kg
    String Mount's dist from hinge: .43m

    The two scenarios change the angles of the rod to the horizontal, and the pulling string to the rod.

    First scenario: Angle to horizontal = 0 degrees, Angle of string to rod = 55 degrees.
    Second scenario: : Angle to horizontal = 47 degrees, Angle of string to rod = 90 degrees.

    2. Relevant equations

    I = (mr^2)/3
    T = Fr(sin [theta]) = I[alpha]

    3. The attempt at a solution

    I have computed all of the torques that I can; they are listed below. My problem is that I don't know how to factor in the instrinsic torque of the rod itself.

    Trqe of W1: .438
    Trqe of W2: 1.297

    Gravity is 9.8m/s^2
    Last edited: Dec 4, 2011
  2. jcsd
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