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Problem with buyoancy and fluid stuff

  1. Nov 25, 2003 #1
    I can't figure this out... I know that answer is wrong, help please? Someone? Ahh!

    http://www.gatcity.com/images2/physics.jpg [Broken]
    Last edited by a moderator: May 1, 2017
  2. jcsd
  3. Nov 25, 2003 #2


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    Staff Emeritus
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    Gold Member

    I guess it's because I haven't TA'd anything yet...

    Can you put down how you went about solving the problem here so we can find where you're having trouble?

  4. Nov 25, 2003 #3

    I figured I needed to find the mass of the wood raft, and then if I had that I could solve what the Fb was.. Originally I thought the buyoant force was 1158 since the net force equals zero and there is a force of 1158 pushing down (that should be 1158 * 9.81)

    ... and then after that I just got really confused and talked to a friend from my class who was equally confused....

    If I can find the mass, then I know that (1158 + m)/(3.40) = density, but I just can't figure out that mass. I've tried all of the buyoant formulas I know, and they aren't helping much...
  5. Nov 26, 2003 #4

    Doc Al

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    Ask yourself what are all the forces acting on the "pig plus raft" system. You know it's in equilibrium, so the net force is zero.

    I see three forces acting:
    Weight of the pig (acts down)
    Weight of the raft (acts down) - how do you figure its weight?
    Bouyant force of water on raft (acts up) - how do you figure bouyant force?

    First figure out all these forces as much as you can. Then write the equation for equilibrium. Then solve for what you don't know.
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