Answer the following question given this paragraph: 

Figure 2.43 Positions and velocities of a metal ball released from rest when air resistance is negligible. Velocity is seen to increase linearly with time while displacement increases with time squared. Acceleration is a constant and is equal to gravitational acceleration.


Q: If a ball is released from rest when air resistance is negligible, velocity is seen to increase linearly, while what related property is a constant?


A:
acceleration