Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Magnitude of a Force on a hatch in a Vessel.

  1. Feb 10, 2009 #1
    1. The problem statement, all variables and given/known data

    We're told the density of ever material involved here, the liquid in the vessel, called "LAB", the water on the outside, and the acryllic that the vessed is made of.
    LAB: 860 kg/m^3
    Water: 1000 kg/m^3
    Acryllic: 1185kg/m^3
    Also, the wall thickness of the vessel is 5.4 cm. The height of the neck is labeled delta h, we're also told to not take the pressure difference between the inside and the outside, due to the 5.4cm wall.

    This is a three part question, but I'm only looking for help on the first part, which asks us to find the force on the hatch, which is 1.00m^2 big, when delta h = 0.

    2. Relevant equations
    We need to use Pressure = Force/Area for this, solving for force gives us
    Force = Pressure*Area
    density * gravity * height = pressure

    3. The attempt at a solution

    My attempt to solve the question, was to solve for the value of pressure of the inside of the system, and then use that to solve for force. Since the height of liquid in the neck is 0, we have no liquid in the neck, so we only have to consider whats inside the circular area, which has a height of 12m, density of 860kg/m^3, and gravity is 9.81 m/s^2, so which we have to add the pressure of 1 atm due to the air at the top, 1.01e-5 Pa.

    Which gives us: 101239 Pa * 1.00 m^2, so the answer is 1.01e5 N?
  2. jcsd
  3. Feb 10, 2009 #2


    User Avatar
    Homework Helper

    But what about the buoyant force from the water beneath the hatch?

    Isn't the pressure there going to be 12m*Δρ*A ?
  4. Feb 10, 2009 #3
    Oops, I accidentally submitted this twice, i had already solved it in another post. Sorry.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook