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Simple Harmonic Motion: Why is acceleration positive at maximum displacement?

  1. Sep 30, 2014 #1
    For example, I have a pendulum with amplitude of 2m, when the pendulum is at a displacement of 2m, wouldn't the acceleration be negative as the restoring force is acting towards equilibrium? The equation I am taught is that maximum acceleration is (2*pi*frequency)^2 * amplitude, which is a positive value?
  2. jcsd
  3. Sep 30, 2014 #2


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    It's the maximal magnitude of acceleration, which always positive. The actual acceleration is a vector, which can point in different directions, depending on the sign of it's components.
  4. Sep 30, 2014 #3
    Oh I see, the book didn't mention that. Thanks.
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