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!

Finding Volume between Two planes Help

  1. Mar 11, 2007 #1
    Finding Volume between Two planes "Help"

    Ok heres the question
    Find the volume of the region between places x+y+2z=2 and 2x+2y+z=4 in THE FIRST QUADRANT, using rectangular coordinates.

    What I have done:

    Graphed the planes. Created x=o y=o and z=o planes to remain in first quadrant for my own visuals. I set both the planes equal to zero. Solved for my x y and z intercepts. x=2, y=2 for both and z=1 for one and z=4 for another.
    Now the set up my integrals. I need to integrate the z to go between the two planes so I was thinking to subtract one from the other..? That or I make me lower limit one of the planes and the other my upper limit. This is whats hanging me up... whether to subtract or not. If it do then its not the same function , but if I dont then I think my limits will have no "limit" to go from z=0 to another limit.

    Help
     
  2. jcsd
  3. Mar 11, 2007 #2
    Everyones lookin and nobodys saying anything. :/
     
  4. Mar 11, 2007 #3

    Tom Mattson

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    One reason for that could be that this isn't the Homework Help section. Allow me to move your thread for you.


    *kick*

    Ah, there we are.

    You mean first octant, don't you? This is 3-space, not 2-space.

    Go with that. Find the volume between each given plane and the xy-plane and subtract the results. You'll need to do a double integral in both cases, but you can treat them as 2 separate mini-problems.
     
  5. Mar 11, 2007 #4
    Im supposed to do a triple integral. Are you saying I should do for dz a integral from O to lower plane - a integral from o to highest... Should I compute for y and x for each of those integrals seperately and subtract two different answers?
     
  6. Mar 11, 2007 #5
    well i get the same answer taking the integral of the lower plane completely and integral of upper plane completely, setting my dy=2-x both times, subtracting two answer= 2.

    then i did a integral subtracting both the planes, y=2-x, x=0..2 and got 2 again.
     
    Last edited: Mar 11, 2007
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Finding Volume between Two planes Help
Loading...