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!

Potential Energy Function

  1. Oct 2, 2008 #1
    A constant force Fx = 6N is in the +x direction.

    A) Find the potential energy function U(x) associated with this force if U(Xo) = 0.

    B) find a function U(x) such that U(4.0m) = 0

    C) Find a function U(x) such that U(6.0) = 14J

    I know that if PE is known then the F can be found by the derivative of the PE.
    I know that if F is known then the PE can be found by integrating the force.

    Since the force Fx is given to be 6N
    the integral of 6 = -6x + C
    Is that PE function for the force Fx?

    Im not sure what A means

    but is B 0 = -6(4) + C
    C = 24?

    and C is 14 = -6(6) + C
    C = 50

    Thanks for your help.
  2. jcsd
  3. Oct 2, 2008 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper

    You have correctly found the constant C, for parts B and C. So you should be able to write the full expression for U(x).

    Part A is done the same way.
  4. Oct 2, 2008 #3
    Thanks! I get it but I have 1 similar problem but I am confused from the context of the problem, if you could help, it be great.

    The force acting on an object is given by Fx = a/x^2. At x = 5.0m, the force is known to point int the -x direction and have a magnitude of 25N. Determine the potential energy associated with this force as a function of x, assuming we assign a reference value of -10J at x = 2.0m for potential energy.

    I know given the force I can take the integral to find the potential energy which is
    integral of a/x^2 since a is a constant I can take it out so it be negative
    integral of 1/x^2 dx = 1/x + C = a/x + C

    The problem is, they are giving me the other information of
    x = 5.0m
    force known to point in -x direction
    x = 2.0

    I do not know what to do with these info. I know they are important. Can someone guide me please, thanks so much.
  5. Oct 3, 2008 #4
  6. Oct 3, 2008 #5


    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper

    You can use the given numbers to get a and C.

    For example,
    F = a/x^2
    You can find a, because you know that F = -25N when x = 5.0m

    Then use your equation for potential energy, and the information about the potential at x=2.0m, to find C.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Potential Energy Function