Arock is thrown downward from an unknown height above the ground with an initial speed of 10m/s. it strikes the ground 3s later. determine the initial

At the beginning of the 3 sec, its speed is 10 m/s.

Over the course of 3 sec, gravity adds (9.8 x 3) = 29.4 m/s
to its speed, so its speed after 3 sec is (10 + 29.4) = 39.4 m/s.

Its average speed during the 3 sec is

                               (1/2) (10 + 39.4) 

                           =  (1/2) (49.4)  =  24.7 m/s .

In 3 sec, at an average speed of 24.7 m/s,
the rock travels

                     (3) x (24.7) = 74.1 meters.

If there's no air resistance in its path, then it was thrown
from 74.1 meters above the ground.

To use anything transparent

The objects do not reach terminal velocity         there is not enough time from the time the object falls from when it hits the ground to achieve terminal velocity. an object must be placed higher to achieve terminal velocity in order to be in free fall.