1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Pressure Cooker Problem

  1. Jan 30, 2009 #1
    1. The problem statement, all variables and given/known data

    A pressure cooker is a sealed pot designed to cook food with the steam produced by boiling water somewhat above 100 C. Consider a pressure cooker with a weight of mass m covering the only hole (which has a diameter d = 0.003 m) on top of it. What should m be in order to cook food at 120 C. Assume the atmospheric pressure outside the cooker is 1 atm.

    2. Relevant equations

    Pressure = Force/Area
    Saturated vapor pressure of water at 120 C = 1.99 x 10^5 Pa

    3. The attempt at a solution

    Since P = F/A, F = AP. F must then at least equal the weight mg of the weight at the top of the pressure cooker in order to lift it and let steam escape. So m = AP/g. The result I get from this approach is incorrect. Any help would be greatly appreciated.
     
  2. jcsd
  3. Jan 30, 2009 #2

    rl.bhat

    User Avatar
    Homework Helper

    Will you please show your calculation?
     
  4. Jan 30, 2009 #3
    PA = mg

    m = PA/g

    where P is the pressure inside the cooker, A is the area of the hole, and m is the mass of the weight.

    [tex]m = \frac{(1.99)(10^{5})(\pi)(0.003^{2})}{(9.8)} = 0.574 kg[/tex]
     
  5. Jan 30, 2009 #4

    rl.bhat

    User Avatar
    Homework Helper

    Have you taken into account the atmospheric pressure?
     
  6. Jan 30, 2009 #5
    Yes, I tried to include the difference in pressures (199,000 Pa - 101,300 Pa) as P in the equation, but still came up with an incorrect answer.
     
  7. Jan 30, 2009 #6

    rl.bhat

    User Avatar
    Homework Helper

    Area = pi*d^2/4
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Pressure Cooker Problem
  1. Pressure Cooker (Replies: 7)

  2. Pressure problem (Replies: 5)

  3. Pressure problem. (Replies: 3)

  4. Pressure problem? (Replies: 1)

Loading...