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Homework Help: A water tank on mars

  1. Jan 15, 2008 #1
    1. The problem statement, all variables and given/known data

    I have a cylindrical water tank of mars, where acc. due to gravity= 3.71

    The pressure at the surface of the water is 110 kPa, and the depth of the water is 14.5 m

    The pressure of the air outside the tank is 91 kPa

    Find the net downward force on the tanks flat bottom of area 2.4 m^2, exerted by the water and air inside the tank and the air outside the tank

    2. Relevant equations

    p= F/A

    3. The attempt at a solution

    alright, I found the downward force to be 3.93x10^5 N
    upward force to be 2.18x10^5

    I thought the sum of these forces would give me the net forces but I must've been mistaken because the answer was wrong.
  2. jcsd
  3. Jan 15, 2008 #2
    You've got the water pushing down, so you need to find the volume of water and figure out the mass(I guess you assume 1 mL= 1g) and mg(but not the normal g!)will be the downward force from the water alone

    Also the air is pushing down on it, as is the outside air, both can be found using your equation

    Don't forget if you use kPa and m^2 you get your answer in kN
  4. Jan 15, 2008 #3
    I know the force from the outside air is 2.18x10^5 N, and the force of the water inside is 3.93x10^5 N, so if I find the force of the air inside the tank as well, the sum of them will give me what I'm looking for?
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