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Homework Help: Force on Mass

  1. Jan 29, 2013 #1
    The position of a mass m = 28.0 kg is given in by x(t) = 3.0sin ((15.0)t). Calculate the magnitude of the maximum force acting on the mass.

    F=ma. I tried deriving x(t) twice to get the acceleration equation so i could plug it into F=ma and then pick a random number for t. I chose t=1 but i still didn't get the right answer.
  2. jcsd
  3. Jan 29, 2013 #2


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    Hint: the maximum value of sin(kt) or cos(kt) is 1 where k is any constant.
  4. Jan 29, 2013 #3
    So I guessed correctly with t=1. But I'm still stumped on where to go from there. Do I still take the 2nd derivative of x(t)?
  5. Jan 29, 2013 #4


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    You are confusing the maximum value of sin(kt) with the value of t.

    If k = 1, is sin (1) a a maximum? Sin (x) and Cos (x) both have maximum values of 1, but the x values where this occurs are different.
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