The acceleration of a ball during its entire time in the air is constant and equal to the acceleration due to gravity, which is approximately 9.8 m/s² downwards.

Here's why:

* Gravity: The only force acting on the ball once it's in the air is gravity. This force pulls the ball downwards, causing it to accelerate.

* Constant Acceleration: The acceleration due to gravity is constant, meaning it doesn't change as the ball travels through the air.

* Direction: The acceleration is always directed downwards, regardless of the ball's initial velocity or trajectory.

Important Note: This assumes there is no air resistance. In reality, air resistance will affect the ball's motion, but for basic calculations, we often ignore it.