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Homework Help: Why did I get it wrong?

  1. Nov 27, 2005 #1
    Here is what I was given in the problem:

    A 0.27 kg mass is suspended on a spring that stretches a distance of 4.9 cm. It is then pulled downward an addtional distance of 12.5 cm and released. Find the displacement from the equilibrium position of the mass (in cm) after 0.42 sec. Count up as positive and g=9.81m/s^2.

    I figured out the spring constant (k=54.06 N/m) and the angular velocity (14.15 s^-1). I then entered the two values I had just found into the displacement equation [x at(t=0.42 s)=A cos (wt)] and got (-12.43 cm). That was wrong. The answer is (-11.78 cm). What did I do wrong? I tried the equation several different ways and got the same answer every time and it was the wrong one.

    Thanks so much for taking the time to help me.:smile:
  2. jcsd
  3. Nov 27, 2005 #2
    Are you using Radian mode when calculating your answer?
    I can find the correct answer by using radian mode.
  4. Nov 28, 2005 #3
    thanks. that was my problem. my calculator was set on degrees instead of radians.:blushing: ooops!
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