When you throw a ball up and it reaches its Apex...

[csx]

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...and the velocity reaches zero. Is the acceleration zero? I am reading that due to gravity it is always non zero in the vertical direction. However, Acc= Velocity/Time. If Acc= 0/Time....should Acceleration not be zero?

 

[tdod]

acceleration is still 10 m/s.

acceleration does NOT equal velocity/time; it equals ∆velocity/∆time. Although the the instantaneous velocity is zero, the velocity is still changing even at the apex.

in sum, acceleration measures the change in velocity, not the velocity itself.

 

[SuperSneaky24]

Acceleration due to gravity on earth is always 9.8m/s^2 in the downwards direction (for MCAT's sake). Acceleration seems like it'z zero because velocity is 0, but remember that your velocity was decreasing as soon as you threw it up. So therefore at that point, velocity may be zero, but it will be decreasing as time moves on due to gravity.