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Weight / Fulcrum problem

  1. Oct 26, 2004 #1

    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" -------->


    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.

  2. jcsd
  3. Oct 26, 2004 #2


    User Avatar
    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. Oct 26, 2004 #3

    That's a big help to me!
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