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!

Which GPE formula is right and when do I use this other

  1. Oct 30, 2015 #1
    In my formula sheet I have written down that

    deltaPEg = (PEg final - PEg initial)

    but then I have written down that

    -(deltaPEg) = (PEg final - PEg initial)

    which one is right?

    Oh and another question, when do I use the formula

    deltaK + deltaPE = 0?
  2. jcsd
  3. Oct 30, 2015 #2


    User Avatar
    2017 Award

    Staff: Mentor

    Depends on the sign convention you like for the energy difference.

    When it is applicable and helps.

    Physics is not about memorizing formulas, it is about understanding how to get the formulas needed to solve the problem.
  4. Oct 30, 2015 #3


    Staff: Mentor

    While I agree with mfb, I do think that the convention for the ##\Delta## symbol is pretty standard. I would always use ##\Delta f = f_{final}-f_{initial}## for any and all ##f##.
  5. Nov 1, 2015 #4

    Mister T

    User Avatar
    Science Advisor
    Gold Member

    When the total mechanical energy of a system is constant (conserved).
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook