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Checking my answers

  1. Oct 27, 2009 #1
    1. The problem statement, all variables and given/known data
    A washing machine that weighs 1400N must be put into a delivery truck bed that is 1.2 m off the ground. A worker uses a force of 450N to push the machine up a ramp that is 4.3m long. What is the efficiency of the inclined plane?

    2. Relevant equations
    e=(MA/IMA)100---- efficiency of a machien in % is = to its mechanical advantage, divided by the ideal mechanical advantage, multiplied by 100.
    MA=Fr/Fe---- mechanical advantage=the resistance of force divided by the effort force.
    IMA=De/Dr----the ideal mechanical advantage of an ideal machien is=to the displacement of the effort force, divided by the displacement of the load.

    3. The attempt at a solution
    MA=1400N/450N=3.11N, I think i did that part right.
    IMA=1.2m/4.3m=0.28m, I think i did this part wrong.
    Last edited: Oct 27, 2009
  2. jcsd
  3. Oct 27, 2009 #2


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    Homework Helper

    Hi Jonathan Teas, welcome to PF.
    First of all MA or IMA are pure numbers. No units for them.
    Next IMA = Distance traveled by effort/ distance traveled load. = ...?
    In Ist or second type of machine IMA cannot be less than one.
  4. Oct 27, 2009 #3
    If IMA= Distance traveled by effort/ distance traveled load
    then IMA= 4.3m/1.2m=3.58 then no unit?
    so the answer is 3.11no unit again/3.58=(0.87)100=87%
    Thank you very much.
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