When the acceleration of a mass on a spring is zero, the velocity is at a
-when the velocity of a mass on a spring is zero, the acceleration is at a

The vibration of a mass attached to a vertical spring, the other end of which is fixed . At the equilibrium position, the velocity is at its maximum and the acceleration  has fallen to zero.

At either position of maximum displacement, the force is greatest and is directed toward the equilibrium position, the velocity  of the mass is zero, its acceleration is at a maximum, and the mass changes direction.

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in physics zero. in muscle fatigue could be high