Final answer:
The value -9.8 m/s² is the acceleration due to gravity (g), directed downward when the upward direction is considered positive.
Step-by-step explanation:
The value -9.8 m/s² represents the acceleration due to gravity on Earth and is commonly denoted as g. When the upward direction is defined as positive, the acceleration due to gravity is given a negative sign (a = -g), indicating that the acceleration is in the downward direction towards the center of Earth. This value of acceleration is applied to objects in free fall where air resistance is negligible, and it allows us to use kinematic equations to analyze their motion.