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Homework Help: Mechanic fluid

  1. Nov 25, 2007 #1
    1)A cup contain 15cm lvl water. A 29cm straw is place into the cup, at the end of the straw is 1cm from the bottom. If a person sucks on the straw, what gauge pressure is needed at the top of the straw to allow the water to run out of the top and into his mouth.

    P=pgh
    1000(9.8) .29 = 2842 Pa

    2) Approximately how deep below the surface of the ocean must a diver go before the absolute pressure on him 2atm.

    P=P0 + pgh
    2atm= 1atm + 1000(9.8)h 1atm=100000 Pa
    100000 Pa= 1000(9.8)h
    h=10m

    3) A body having a density of 300kg/m^3 is floating in a container of liquid. If 1/3 of the volume of the body remains above the surface of the liquid, what is the density of the liquid?
    1/2*300=100kg/m^3
    100+300= 400 Kg/m^3
     
  2. jcsd
  3. Nov 25, 2007 #2
    i need advice plz
     
  4. Nov 26, 2007 #3
    anyone?
     
  5. Nov 26, 2007 #4
    1. P0 = P+ pgh
    P = P0 - 1000(9.8) .29
     
  6. Nov 26, 2007 #5
    P=pgh
    2atm=1000(9.8)h shud nt take atmosph press. because inside water it acts in all dir. hence cancels
     
  7. Nov 26, 2007 #6
    3. P*2/3=300
    3/2*300=450
     
  8. Nov 26, 2007 #7
    ty
    I got the last 1 still trying to figure out and may be u can help
    10kg raft made of driftwood w/ specific gravity .60 floats on the surface of a calm pond. Density of water = 1000 kg/m^3
    Calculate the volume of the raft

    Im not sure if the problem missing some unit
    I need Density of the raft to calculate the Volume
    I dont know how to get there. Any idea?
     
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