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Homework Help: Fluid statics question

  1. Nov 6, 2016 #1
    1. The problem statement, all variables and given/known data
    A 1,500-kg car stands on a square platform, and a 25-kg boy stands on another square platform. These platforms are the two caps of a large oil-filled container. What must the ratio of the platform sides (large/small) for the boy to gently lift the car?

    -less than 1.5
    -Between 3.0 and 4.4
    -More than 6.0
    -Between 1.5 and 2.9
    -Between 4.5 and 6.0

    2. Relevant equations
    Fsmall= (Asmall/Alarge)*Flarge

    3. The attempt at a solution

    25*9.8 = (Asmall/Alarge)*(1500*9.8)
    Asmall/Alarge =1/60
    I know this is definitely not the right ratio, and I know I'm not including something probably in the area portion -I'm just not sure what that is
  2. jcsd
  3. Nov 6, 2016 #2


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    How is the ratio of "the platform sides" related to the ratio of the areas?
  4. Nov 6, 2016 #3
    I'm not sure, so the ratio of the platform sides would be different from the ratio of the areas, but I have no clue how you would decipher between the two...
  5. Nov 6, 2016 #4


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    The platforms are in the shape of a square. How do you calculate the area of a square if you know the length of the sides?
  6. Nov 6, 2016 #5
    Oh I missed that it would be a square so you'd take the square root of the area ratio?
  7. Nov 6, 2016 #6
    Thanks that was right!
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