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Force required to lift beam

  1. Aug 16, 2006 #1
    I have another question maybe someone can help me with. I have attached a drawing of a beam (tube) that is 42" long and weighs 50 lbs. The beam pivots at one end (red dot). If the beam weighs 50 lbs how much force is required to lift the beam to a vertical position if I apply force at a 45 degree angle, 12 inches from the pivot point? If anyone has a formula I would appreciate it as I would like to play around with the angle and distance of applied force. Thanks again!

    Attached Files:

    • beam.bmp
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  2. jcsd
  3. Aug 16, 2006 #2


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    Staff Emeritus
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    This is simply a moment problem.

    The mass of the beam acts at the mid point, so apply mg at 21", and the force at 12" must be such that the moment at 21" is exceeded by the moment at 12".

    The moment is a normal force * moment arm (length).

    Since the problem imposes a force at 45° to the beam, then one must determine the component normal (perpendicular) to the beam. Similarly, as the beam rotates upward, the normal component of the weight changes because the axis of the beam is rotating in the gravitational field.

    This problem belongs in the Engineering, Technology, . . homework section.
  4. Aug 17, 2006 #3

    Thanks! Thats what I thought (moment problem). After I typed it out I started wondering if I was overthinking it :yuck: Thanks again, I appreciate the help.
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