Here's why:
* Acceleration is the rate of change of velocity. Velocity includes both speed (how fast an object is moving) and direction.
* Positive acceleration means an increase in speed or a change in direction that results in a higher speed.
* Negative acceleration (also called deceleration or retardation) means a decrease in speed or a change in direction that results in a lower speed.
Think of it this way:
* If you're driving a car and you press the gas pedal, you are accelerating.
* If you press the brakes, you are decelerating (negative acceleration).
