Answer: The gravity's constant value is
.
Step-by-step explanation:
The given function shows the distance from the ground (in meters) at time t (in sec).

First derivative of displacement is velocity and the second derivative of displacement is acceleration.
Differentiate the given equation with respect to t.

Differentiate the above equation with respect to t.

It is given that gravity is the only acceleration affecting the object and the negative sign shows the downward direction of the object.
Therefore, the gravity's constant value is
.