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

[pyman12]

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?

 

[A.T.]

The equation I am taught is that maximum acceleration is (2*pi*frequency)^2 * amplitude, which is a positive value?

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.

 

[pyman12]

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.

Oh I see, the book didn't mention that. Thanks.