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Homework Help: Torque around a beam

  1. Apr 19, 2015 #1
    1. The problem statement, all variables and given/known data

    Two 8.0N forces act at each end of a beam of length 0.60m. The forces are parallel and act in opposite directions. The angle between the forces and the beam are 60 degrees.

    What is the torque of the couple exerted on the beam?

    1. 2.4Nm
    2. 4.2Nm
    3. 4.8Nm
    4. 9.6Nm

    2. Relevant equations

    From my understanding: Torque = Fdsinθ, where F is the force and d is the distance from the force

    3. The attempt at a solution

    I tried to apply the equation (as above) in this example:

    Torque = Fdsinθ = 8.0 * .30m * sin(60) ≈ 2.07

    However, this isn't one of the given options so I feel I must be doing something wrong.

    Any help is greatly appreciated!
  2. jcsd
  3. Apr 19, 2015 #2


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    Don't forget that there are 2 forces.
  4. Apr 19, 2015 #3
    So do I multiply my answer by two? 2.07 * 2 ≈ 4.15

    Therefore is the correct answer rounded up to Option 2. - 4.2Nm?
  5. Apr 19, 2015 #4


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    Yes, the torque due to the couple is the net torque due to both forces.
    I think that's correct.
  6. Apr 19, 2015 #5
    Thank you - that makes sense to me now! :)
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