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Maximum acceleration

  1. Jul 4, 2017 #1
    1. The problem statement, all variables and given/known data
    *Forgot to mention that this is a SHM question in the title
    Which of the following statements about an object that which perform an Simple harmonic motion is true?
    A) the acceleration is maximum when the velocity is maximum
    B) the acceleration is maximum when the displacement is maximum
    C) the maximum potential energy is greater than the maximum kinectic energy
    D) the maximum kinectic energy is greater than the maximum potential energy

    2. Relevant equations
    x= A sin wt
    v= Aw cos wt
    a= Aw^2 sin wt

    3. The attempt at a solution
    At first i was choosing a because i believe c and d is not possible due to conversation of energy. But then i feeling like something wasn't right, so i went to check my references book on the graphs of x,v,a against t.
    Which i found out that when a is maximum, v is 0 and when a is 0, v is maximum. So i change my answer to b. But the answer given is a. So i wonder why is it a
    SHM1.gif
     
  2. jcsd
  3. Jul 4, 2017 #2

    Orodruin

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    B is correct. Just note that you missed a minus sign in your acceleration expression. The graph is qualitatively correct. A is false.
     
  4. Jul 4, 2017 #3
    Oh yeah i forgot to put the minus sign. Thanks for the quick answer
     
  5. Jul 4, 2017 #4

    Orodruin

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    Also note that while answers C and D are both false with the standard choice of potential energy being zero at zero displacement from the equilibrium (the correct thing being that the maximum potential is equal to the maximum kinetic energy with that choice of potential), there is nothing stopping you from arbitrarily redefining the zero level of the potential energy. If you do, either C or D could be made to be correct.
     
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