# Simple harmonic motion

When observing the acceleration graph of simple harmonic motion we can see that the acceleration is just the opposite of the elongation. Yet we know that the pendulum velocity is increasing when approaching the equilibrium state. Which means that the motion is accelerated altough the sign of the acceleration is negative. How to understand this contradiction?

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Bim said:
When observing the acceleration graph of simple harmonic motion we can see that the acceleration is just the opposite of the elongation.
The restoring force, and the resulting acceleration, always points towards the equilibrium point.
Yet we know that the pendulum velocity is increasing when approaching the equilibrium state.
That's what acceleration does! Which means that the motion is accelerated altough the sign of the acceleration is negative.
The acceleration is always toward the equilibrium point. Thus when the object moves towards equilibrium, its speed increases: both its acceleration and velocity will have the same sign. (Both negative on one side of equilibrium, both positive on the other.)

Realize that something with a negative velocity and a negative acceleration will speed up.