In a vacuum, a ball falls solely under the influence of gravity. There is no air resistance to oppose its motion. The ball accelerates downward at a constant rate of 9.8 meters per second squared near Earth's surface.
In a vacuum, only one force acts on the falling ball: gravity. The gravitational force equals mass times gravitational acceleration. There is no air resistance because there are no air molecules to create drag force.
With only gravity acting, the ball experiences constant acceleration of 9.8 meters per second squared. This means its velocity increases steadily as it falls. The velocity equals gravitational acceleration times time.
In a vacuum, all objects fall at exactly the same rate, regardless of their mass or shape. A heavy ball and a light ball will fall together and hit the ground simultaneously. This demonstrates that gravitational acceleration is independent of mass.
To summarize: In a vacuum, a ball falls under gravity alone with constant acceleration of 9.8 meters per second squared. There is no air resistance, so all objects fall at the same rate regardless of mass. The motion follows simple kinematic equations for uniformly accelerated motion.