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Homework Help: Does this question make sense?

  1. Jun 21, 2016 #1
    [Note: Thread moved from General Physics, so no template is shown]

    Sorry guys, beginner here taking an online introduction physics course. I'm on a unit involving torque and force. The computer lab taught me how to calculate the force needed to balance a seesaw type setup on the left side, with a given weight on the right side. Easy enough. But one of the questions my instructor has given me seems a bit different, or maybe I'm not getting the point..

    "Use the sum of vertical forces and torque equations to calculate the force at the Left and Right end of a 10 foot long plank that has a 200 lb weight 3 ft from the left end.."

    Shouldn't there be some type of axis that the plank sits on?

    Any help would be much appreciated

    Thanks guys!
  2. jcsd
  3. Jun 21, 2016 #2
    Imagine the plank suspended by ropes at the end, like a scaffold.
    Or simply supported on two bricks placed at the ends.
    It does not matter how the forces at the ends are produced. But it may help to imagine some specific situation.
  4. Jun 21, 2016 #3


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    It would help if you included the entire problem statement verbatim.

    It's not clear how this plank is supported, i.e. at one point somewhere along the length, or at each end.
  5. Jun 21, 2016 #4
    This is why I posted the question. This is all the info I was given, no picture included.
  6. Jun 21, 2016 #5
    I think this shines a bit of light on what I'm looking for. So if there is a 200 lb weight 3 ft from the left end, this would produce 600 ft lbs of torque on the left end? Or is that not the correct measurement since it is looking for force? Physics is going to be the death of me lol.
  7. Jun 21, 2016 #6
    Nvmd, that's clearly not right
  8. Jun 22, 2016 #7
    Something tells me I'm thinking backwards, So would it be 200/3 for the left side?
  9. Jun 22, 2016 #8


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    Staff: Mentor

    I've moved this to the Introductory Physics Homework section. Further homework questions should be posted here and the template should be used (it will be in the reply box when you start a new thread in the homework forums).
  10. Jun 22, 2016 #9


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    There are two unknowns (the forces on each end) so you need two equations.

    What do you know about the forces and torques acting on static objects?

    I would start with a free body diagram.
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