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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.

    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

    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?
    100+300= 400 Kg/m^3
  2. jcsd
  3. Nov 25, 2007 #2
    i need advice plz
  4. Nov 26, 2007 #3
  5. Nov 26, 2007 #4
    1. P0 = P+ pgh
    P = P0 - 1000(9.8) .29
  6. Nov 26, 2007 #5
    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
  8. Nov 26, 2007 #7
    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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