1. Limited time only! Sign up for a free 30min personal 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!

Work lifting cable and work pumping water

  1. Mar 2, 2010 #1
    so i know that when there is a cable hanging from say a building that is taller than the length of the cable and you want to find the work done lifting half of the cable, you have to split the integral up since each "small piece" of rope in the first half gets lifted up a variable amount while each "small piece" of rope in the 2nd half gets lifted the same amount.

    now when you are finding the work done by pumping water, lets say the problem is to find the work done in pumping water out of the top of the container so that only a depth of 1 ft of water remains. would you have to split up the integral in a similar way to the cable problem described above? or could you just adjust the limits of integration accordingly. for example if the tank is 4 ft tall and the limits to find the work to pump out all the water is from 0 to 4. could you change it so that the limits become from 0 to 3 to find the work needed to pump the water out so that 1ft depth remains?
  2. jcsd
  3. Mar 2, 2010 #2


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    The center of mass of the water you are pumping out has to reach the height of the tank.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook