Here's why:

* Acceleration is the rate of change of velocity over time.

* Velocity is the rate of change of position over time, measured in meters per second (m/s).

* Therefore, acceleration is measured in meters per second per second, or meters per second squared (m/s²).

Gravitational acceleration is the acceleration experienced by an object due to the force of gravity. On Earth, the standard value for gravitational acceleration is approximately 9.81 m/s².