Here's why:
* Acceleration is the rate of change of velocity.
* Velocity is a vector quantity, meaning it has both magnitude (speed) and direction.
* If the speed is increasing, the magnitude of the velocity vector is getting larger.
* Since acceleration is the rate of change of velocity, a positive acceleration indicates that the magnitude of the velocity vector is increasing.
Important Note: The sign of acceleration doesn't always indicate whether an object is speeding up or slowing down. If the object is moving in the negative direction and its speed is increasing, its acceleration would still be negative.
