Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Rotational Statics Of A Balance Beam

  1. Nov 9, 2011 #1
    1. The problem statement, all variables and given/known data
    A gymnast with mass m1 = 48 kg is on a balance beam that sits on (but is not attached to) two supports. The beam has a mass m2 = 121 kg and length L = 5 m. Each support is 1/3 of the way from each end. Initially the gymnast stands at the left end of the beam.
    1)What is the force the left support exerts on the beam?

    2. Relevant equations


    3. The attempt at a solution

    So I just solved a problem where I solved for the tension in a string holding up a beam attached to a wall...etc. I am not really sure how to transfer the same equations to this situation. So far I know that the net force and net torque on the system is zero. So for example I know that a hinge in the other problem acts a net force of Mass of the beam by the gravity. Not really sure what formula to use for the beams.
  2. jcsd
  3. Nov 9, 2011 #2


    User Avatar
    Homework Helper

    You can indeed use torques, and take them about any point you choose.

    All you need is the size of the force, and the distance from its [effective] point of action to your chosen reference point.

    Since you don't know the force provided by either support - choosing one of them as you rotational reference is the most logical.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook