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Parallel Forces: Painter on scaffold x meters from 1 end.

  1. Aug 23, 2015 #1

    My book says that although there is a natural point of rotation, we can however choose any point as a center of rotation. But without explaining further, it goes directly to an example where the endpoint is the center of rotation.

    I would like to know what the book means by being able to choose any point as a center of rotation.

    For example,
    A painter weighing 150lbs is standing on a 6ft scaffold at a distance of 2 ft from one end. How much weight must each end of the scaffold hold?

    F1 + F2 = 150lbs

    Torque = Torque
    Fs = Fs
    150lbs(2ft) = F2(6ft)
    F2 = 50lbs

    So F1 + F2 = 150lbs
    F1 + 50lbs = 150lbs
    F1 = 100lbs

    Here, F1 was the point of rotation. But how can this problem be approached if a different point of rotation is considered? And is there an infinite number of choices for points of rotation? Or is there a finite number of possible points/centers of rotation?
  2. jcsd
  3. Aug 23, 2015 #2


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    Homework Helper

    Let's say you chose a point of rotation on the scaffold, 0<x<6.
    Then if F1 is placed at 0 and F2 placed at 6, you still have to balance the forces.
  4. Aug 28, 2015 #3
    Thank you RUber.
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