Weight / Fulcrum problem

  1. Hi,

    I am a non-physics type that needs an answer to a fairly simple physics problem (but too complex for me). I need to know where to place a weight on a trailer to arrive at a specific tongue weight (weight at the hitch).

    I hope the diagram below is clear.

    <------ 48" ------->
    -------- W --------

    H ------------------------------------- A --------------------- E
    <---------------- 96" -----------------> <-------- 64" -------->

    Notes:

    Line H/A/E is the trailer.

    W represents a 1600 lb weight that is 48" wide and is centered over the axle.

    The trailer is perfectly balanced at this point (no weight at point H).

    H represents the trailer hitch.

    A represents the axle (fulcrum).

    E represents the end of the trailer.

    The distance from H to A is 96".

    The distance from A to E is 64".


    PROBLEM: How far would the weight (W) need to be moved to the left to arrive at a tongue weight (weight at point H) of 250 lbs?

    I hope someone can figure this out. I am stumped.

    Thanks in advance.

    Jody
     
  2. jcsd
  3. Integral

    Integral 7,351
    Staff Emeritus
    Science Advisor
    Gold Member

    The torque about the axels must be the same at all points on the trailer so the force * distance is the same at all points. x is the location of the center of your load.

    [tex] 1600 x = 250 * 96 [/tex]

    [tex] x = \frac {250lb * 96in} {1600lb} = 15in [/tex]
     
  4. Thanks

    That's a big help to me!
     
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