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!

Gravitational potential energy of a system

  1. Nov 30, 2013 #1
    1. The problem statement, all variables and given/known data
    What is the gravitational potential energy of a system of 8 masses of 10 kg each placed at the corners of a cube of length 0.25 meter apart.



    2. Relevant equations
    U=-G*m1*m2/r


    3. The attempt at a solution
    I have actually taken one particle pair at a time and sum all of their potential energy, but the answer is not quite right.
     

    Attached Files:

  2. jcsd
  3. Nov 30, 2013 #2

    Simon Bridge

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    2016 Award

    You just want to find the work needed to remove all the masses to infinity.
    So pick one ... remove it: how much work would that take?

    OK so now you have 5 masses - pick one, remove it: how much work did that take?

    Rinse and repeat.
     
  4. Nov 30, 2013 #3
    I think there are 8 masses in here.
     
  5. Nov 30, 2013 #4

    Simon Bridge

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    2016 Award

    Good - you are paying attention ;)
    How would you have to change the suggestion to account for the different number of masses?
     
  6. Nov 30, 2013 #5
    I think it will be very tiresome to pick each and every particle and work out their work done in bringing them from infinity to that position. There must be some quick method.......
     
  7. Nov 30, 2013 #6

    Simon Bridge

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    2016 Award

    Yes and no - there is no getting around having to do this for every particle.
    But you only have 8 steps to do, and, once you get started, you should notice a pattern that makes things easier.

    Finding this out is a big part of why the exercize is set in the first place.
    There is no Royal road to knowledge.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted