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Simple Harmonic Oscillation Problem

  1. Jun 19, 2013 #1
    1. The problem statement, all variables and given/known data
    The velocity of an object in simple harmonic motion is given by v(t)= -(4.04m/s)sin(21.0t + 1.00π), where t is in seconds. What is the first time after t=0.00 s at which the velocity is -0.149m/s?

    2. Relevant equations

    3. The attempt at a solution
    I thought this was an easy question but there must be a flaw somewhere in my logic. I've tried -0.149=-4.04*sin(21t+pi). However, solving for t gives me a negative number. I've also tried doing using cos instead of sin to get rid of the phase constant, but still the wrong answer. It's given me aprrox. 0.07s. Any help would be appreciated
  2. jcsd
  3. Jun 19, 2013 #2
    A couple of suggestions.
    If you change the argument of sin by 2Pi what happens.
    You might also use a graphing calculator to plot the function to get some insight as to what is going on.
  4. Jun 19, 2013 #3
    Nothing happens if you change it by 2Pi? Since thats one full cycle. But this is 1pi?
  5. Jun 19, 2013 #4
    You probably found the sin^-1 of .149/4.04 and that gave you a negative t. Could you change the 1pi to -p1 and resolve?
  6. Jun 19, 2013 #5
    Of course you can, because its a cycle. Appreciate the insight.
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