What is Acceleration?

Acceleration is the rate at which velocity changes. If you are in a car and the driver steps on the accelerator to overtake, your velocity increases—you are accelerating.

But be careful! You are also accelerating if you hit the brakes (that is negative acceleration, or deceleration). You are ALSO accelerating if you just turn a corner at a constant speed, because your direction is changing, which means your velocity is changing!