Question

The velocity of a ball as it is thrown up is 20 meters/second. It attains zero velocity after 3.5 seconds. What is the average acceleration of the ball during its upward flight?

Answer 1

Change in speed = (speed at the end) minus (speed at the beginning)

                           =                    (0 - 20 m/s)  =  -20 m/s

Acceleration = (change in speed) / (time for the change)

                           =  (-20 m/s)      /   (3.5 sec)   =   -5.71 m/s²

Notice that this story probably didn't happen on Earth, because
the acceleration due to gravity on Earth is  9.8 m/s².