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Homework Help: Applying work energy theorem to unifrom circular motion

  1. Aug 27, 2016 #1
    1. The problem statement, all variables and given/known data
    attempt to derive the equation of centripetal acceleration using work energy theorem

    2. Relevant equations

    work done = Change in kinetic energy

    3. The attempt at a solution

    consider diametrically opposed points occurring in uniform circular motion - displacement = 2*R and let force be denoted by F

    By work energy theorem ; F*2R = 1/2mv^2 - (-1/2mv^2)
    F = mv^2/2R

    So close...
    Where did I go wrong
  2. jcsd
  3. Aug 27, 2016 #2

    Doc Al

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    Staff: Mentor

    In uniform circular motion, the force and displacement are always at right angles--no work is done.
  4. Sep 6, 2016 #3


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    Science Advisor
    Homework Helper
    Gold Member

    Also, kinetic energy is not a vector. It is incorrect to say that kinetic energy is positive when the mass is moving in one direction and negative when moving in the opposite direction.
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