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HELP A problem on oscillation

  1. Jan 14, 2009 #1
    HELP!!!A problem on oscillation

    The problem statement, all variables and given/known data
    the equation of motion of an object is y(t)=2.0cos(0.5t+pi/4)meter
    a) Find its maximum acceleration and maximum speed, and its position at the time of these maxima.
    b) what is the speed of the object when it is +1.2m from its equilibrium position?
    c) what are the kinetic potntial and total energies at that point?

    The attempt at a solution
    a) for this part I don't reall understand what does the question mean by the maximum, is it when cos equals to 1?
    b) derive 2.0cos(0.5t+pi/4), which equals to -2sin(0.5t+pi/4)*0.5=-1sin(0.5t+pi/4)
    then plug the 1.2 into the unknown variable, which equals to -sin(0.5*1.2+pi/4)=-0.98 I don't really think it is the correct solution for this part
    c) I have to find out the correct v from part B and plug into both kinetic and potential energy equation, but I have one more problem here, which is how do i get mass for this question?
    P((1/2mv^2)i) + K(1/2mv^2)i) = P((1/2mv^2)f) + K(1/2mv^2)f)

    Thank you for helping me.
  2. jcsd
  3. Jan 14, 2009 #2


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    Homework Helper

    Re: HELP!!!A problem on oscillation

    You're given the equation for motion.

    velocity is the first derivative.

    acceleration is the second derivative.

    At what value of t then do each of these functions reach their max?
  4. Jan 14, 2009 #3
    Re: HELP!!!A problem on oscillation

    Sorry, but i still don't quite understand what does max mean, does it mean that when cos or sin equals to 1?
  5. Jan 14, 2009 #4


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    Homework Helper

    Re: HELP!!!A problem on oscillation

    I'd say so.
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