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Homework Help: How many people can the raft hold physics problem

  1. Oct 4, 2008 #1
    CAN ANYONE HELP ME, PLEASE ! I DON'T KNOW HOW TO SOLVE THIS PROBLEM

    A raft is made of 10 logs lashed together. Each is 30cm in diameter and has a length of 5.5m. How many people can the raft hold before they start getting their feet wet,assuming the average person has a mass of 70 kg? Do not neglect the weight of the logs! Assume the specific gravity of wood is 0.60.

    SG=0.60
    r=1/2*30=15cm

    I know
    F/A = mg/A
    F= mg =pAHg were p-->density
    p=m/v
    pressure=P=F/A
     
  2. jcsd
  3. Oct 4, 2008 #2

    Doc Al

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    Staff: Mentor

    Re: Fluids

    Hint: What's the buoyant force acting on a completely submerged log?
     
  4. Oct 4, 2008 #3
    Re: Fluids

    The boyanty Force is:

    Fb = F2 - F1
    pfgA(h2-h1)
    pfgAh
    pfgV

    I don't know how to solve please help !
     
  5. Oct 4, 2008 #4

    Doc Al

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    Staff: Mentor

    Re: Fluids

    The buoyant force is the weight of the displaced fluid. How much water does a submerged log displace?
     
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