1. PF Contest - Win "Conquering the Physics GRE" book! Click Here to Enter
    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!

Differentiation of potential energy

  1. Mar 14, 2008 #1
    1. The problem statement, all variables and given/known data

    The potential energy of a system of two particles separated by a distance r is given by U(r) = (A)/(r^4), where A is a constant. Find the radial force that each particle exerts on the other. (Use A and r as appropriate in your equation.)

    2. Relevant equations

    U is potential energy

    3. The attempt at a solution

    i figured out the antiderivative of U(r) is -(A)/(3*r^(3)) but it isnt the correct answer.
    what else do u need to do besides the antiderivative which is equal to force. since it is 2 particles should i divide the U(r) funciton by 2?
    Last edited: Mar 14, 2008
  2. jcsd
  3. Mar 14, 2008 #2
    you actually want the partial derivative of r
  4. Mar 14, 2008 #3
    ok but how do u get that? im rather new at the whole calculus thing. wud it just b A/3r^3?
  5. Mar 14, 2008 #4
    Think of U(r) as A*(r^-4) then try to differentiate it...
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook