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Homework Help: Finding the density of a liquid with buoyancy

  1. Nov 13, 2006 #1
    A rectangular block is gradually pushed faced-down into a liquid. The block has height d; on the bottom and top the face area is A=5.67 cm^2 . Also shown is a graph that shows the apparent weight W_app of the block as a function of the depth h of its lower face. What is the density of the liquid in units of g/cm^3

    Originally I used the equation B=p(fluid)ghA and solved for the density of the fluid. First of all, is this the right equation to use?
  2. jcsd
  3. Nov 13, 2006 #2
    I can't for some reason post the figures but if anyone can still give me some help without the use of the figures would be greatly appreciated.
  4. Nov 13, 2006 #3


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    Apparent weight W_a is actual weight W minus the buoyant force B.

    W_a = W - B

    I assume your graph starts with W_a = 0 at some h and then goes down as h increases. The buoyant force is the Area of the face times the pressure (ρgh), as you have written it. Everything in B is a constant except for h, and W is a constant. The equation above is the equation of a straight line. There is a connection between the slope of that line and the constant factors in B. What is that connection?
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