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Simple question - Archimedes principle

  1. Feb 15, 2010 #1
    An object weighs 30kg in air it is lowered into a square tank (1m x 1m)
    the weight of the object in the water is 16kg. how much does the water level in the tank raise?


    Heres my attempt.
    30-16 = 14kg

    14kg = 14 m^3

    1 x 1 x h = 14

    h = 14 metres.

    Is this correct it doesnt seem right for some reason??

    Thank you for your time
     
  2. jcsd
  3. Feb 15, 2010 #2

    Borek

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    Staff: Mentor

    Way too much. What is water density?
     
    Last edited by a moderator: Aug 13, 2013
  4. Feb 15, 2010 #3
    1000 kg/m^3 = rho

    so W/1000 x 9.81 = h?????

    =14000/9810 = 1.43m???

    Thanks for the help
     
  5. Feb 15, 2010 #4

    Borek

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    Staff: Mentor

    Worst approach you can take it to calculate first, apply units later. That's what you are doing and your answer is all the time wrong.
     
    Last edited by a moderator: Aug 13, 2013
  6. Feb 15, 2010 #5
    I dont understand? do you mean my formula is correct but my units are wrong?

    14/98100= 1.43 x 10^-3???
     
  7. Feb 15, 2010 #6

    Borek

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    Staff: Mentor

    What is what of what?

    Numbers you present - as long as they don't have any units - don't make any sense.
     
    Last edited by a moderator: Aug 13, 2013
  8. Feb 16, 2010 #7
    14kg / (1000kg/m^3 x 9.81m/s)= 1.43 x 10^-3 m
     
  9. Feb 16, 2010 #8
    I guess the text of the problem creates some confusion. They call the 30 kg "weight" but it's the mass actually.
    What is the weight of the water displaced? Not the mass.
     
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