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!

Question dealing with density and pressure

  1. Jan 18, 2009 #1
    I haven't taken physics in a while, and most of this is physics related. My professor's lectures have not helped me understand the material, so I have questions on my homework. I would like to learn how to approach this problem and solve it.


    The figure shows a vertical dam holding back a reservoir of depth h. The lower half of the reservoir consists of a sludge whose density is twice that of water, and the upper half of the reservoir's volume consists of pure water.

    a. Determine how pressure depends on altitude z in the water and sludge.
    b. Let w be the dam's width, and determine the horizontal component of force on the dam.


    Thank you in advance.
     

    Attached Files:

  2. jcsd
  3. Jan 18, 2009 #2

    tiny-tim

    User Avatar
    Science Advisor
    Homework Helper

    Welcome to PF!

    Hi tophat22! Welcome to PF! :smile:
    a. The pressure is basically the weight of the fluid above (per area). :smile:

    b. Pressure = force per area, so the force on the dam is the integral of pressure times area. :wink:
     
  4. Jan 19, 2009 #3
    for part a, what am I supposed to do with vector z? will I have to deal with an integral?
     
  5. Jan 19, 2009 #4

    tiny-tim

    User Avatar
    Science Advisor
    Homework Helper

    Hi tophat22! :smile:
    No, you'd only need an integral if the density was varying continuously

    but here, it's constant to a certain height, and then a different constant, so you can just multiply instead of integrating. :smile:
     
  6. Jan 20, 2009 #5

    stewartcs

    User Avatar
    Science Advisor

    Since the pressure varies with depth there will be a different force on the dam at different depths. So integration would be needed.

    CS
     
  7. Jan 20, 2009 #6

    tiny-tim

    User Avatar
    Science Advisor
    Homework Helper

    Hi stewartcs! :smile:

    Not for part a. :wink:
     
  8. Jan 20, 2009 #7

    stewartcs

    User Avatar
    Science Advisor

    Sorry I missed the "part a" there! :blushing: Silly me...I should not post until my morning tea!

    CS
     
  9. Jan 20, 2009 #8

    tiny-tim

    User Avatar
    Science Advisor
    Homework Helper

    It's afternoon here in London! :biggrin:

    'll soon be proper tea-time

    … and time for "Countdown" on telly. :tongue2:​
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Question dealing with density and pressure
  1. Pressure and density (Replies: 1)

  2. Pressure and Density. (Replies: 2)

  3. Density and pressure (Replies: 1)

  4. Pressure and density (Replies: 2)

Loading...