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Homework Help: Potential Energy and force

  1. Dec 9, 2007 #1
    1. The problem statement, all variables and given/known data

    An object of mass 0.5 kg experiences a force that is associated with the potential energy function
    U(x) = 4/ 2+x , where U is in joules and x is in meters.
    a. On the axes below, sketch the graph of U(x) versus x.

    (graph) Y aixs U(J), x axis x(m)

    b. Determine the force associated with the potential energy function given above.
    c. Suppose that the object is released from rest at the origin. Determine the speed of the particle at x = 2 m.

    In the laboratory, you are given a glider of mass 0.50 kg on an air track. The glider is acted on by the force determined in part b. Your goal is to determine experimentally the validity of your theoretical calculation in part c.

    d. From the list below, select the additional equipment you will need from the laboratory to do your experiment by checking the line to the left of each item. If you need more than one of an item, place the number you need on the line.

    Meterstick _____ Stopwatch Photogate timer String Spring

    Balance Wood block Set of objects of different masses

    2. Relevant equations


    3. The attempt at a solution

    On a I think you just draw the graph so I'm okay with that one. ;)

    On b what force are they talking about? I didn't think PEg was a force..
  2. jcsd
  3. Dec 9, 2007 #2
    To answer part (b), the force associated with a potential energy is given by:

    F= - dU/dx

    So I think you just need to differentiate the equation you're given for the potential energy, U(x), and then take the negative of it.
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