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Homework Help: Torque AP Practice Problem

  1. Dec 13, 2009 #1
    1. The 1.0-m-long nonuniform plank has weight 1000 N. It is supported by two rods, A and B, as shown above. The center of mass of the plank is 30 cm from the right edge. Each support bears half the weight of the plank. If support B is 10 cm from the right-hand edge, how far from the left-hand edge should support A be?

    The attached image is the picture for this problem that was given.

    2. torque (clockwise)=torque (counterclockwise)

    3. This is a multiple choice question and the choices are : 0 cm, 10 cm, 30 cm, 50 cm, and 70 cm. I have no idea how to do this problem so help would be appreciated.

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  2. jcsd
  3. Dec 13, 2009 #2


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    The support forces are given as 500 N each. So just use your equation to solve, by summing torques about the right support. Be sure to draw a sketch properly showing all dimensions.
  4. Dec 13, 2009 #3
    Do you think the questioner could expect a student to solve this problem mentally?

    When you've solved the problem formally, look for a simpler way of getting the same result.
    Hint - when the support forces are equal, how far is the centre of mass from each support?
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