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Kinetic Energy Plot

  1. Apr 19, 2009 #1
    1. The problem statement, all variables and given/known data

    Figure shows a plot of potential energy U versus position x of a 0.900 kg particle that can travel only along an x axis. (Nonconservative forces are not involved.) Three values are UA = 15 J, UB = 35 J and UC = 45 J. The particle is released at x = 4.5 m with an initial speed of 6.80 m/s, headed in the negative x direction.

    If the particle can reach x = 1.0 m, what is its speed there, and if it cannot, what is its turning point?

    http://edugen.wiley.com/edugen/courses/crs1650/art/qb/qu/c08/q39.jpg [Broken]

    2. Relevant equations


    3. The attempt at a solution

    I have no clue what to do.
    Last edited by a moderator: May 4, 2017
  2. jcsd
  3. Apr 19, 2009 #2
    What is the particle's total energy at t = 0?
  4. Apr 19, 2009 #3
    they don't give time, help anyone?
  5. Apr 19, 2009 #4
    Let me rephrase, what is the particle's total energy?
  6. Apr 19, 2009 #5


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    Homework Helper

    Find the KE at 4 m.
    UB - UA = KE at 4m - KE at 2m
    If it is positive, the particle will reach 1 m.
  7. Apr 9, 2011 #6
    Hi, I am also having trouble with this problem. It is not homework, I am doing it out of the book.

    So I am trying to find the speed at x=1m

    Why would KE at 1 m not be Uc - Ub? Isn't KE the space inbetween the U line and the total energy?

    Just in case last person pic doesn't work any more here is my own link from book:


    And after I find the KE I use
    KE = 1/2 mv^2 to find the velocity

    I didn't find the right velocity when I took Ub-Ua.
    I also didn't find the right velocity when I took Uc - Ub.

    The answer should be : 2.1 m/s

    How do I get this?
  8. Apr 9, 2011 #7
    would it have been better to start a new thread for my question? This last question is over a year old....

    Any advice helps. Thank you! :)
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