Stephanie serves a volleyball from a height of

0.78 m and gives it an initial velocity of +7.7
m/s straight up.
How high will the volleyball go? The acceleration of gravity is 9.81 m/s^2.

How long will it take the ball to reach its
maximum height?

1 answer

It travels up untils its vertical velocity is zero. That happens after t = 7.7/g = 0.785 seconds. (That answers your second question). During that time, it moves upward
t*Vaverage =
(1/2)*(7.7)*(0.785) = 3.02 m

Add that to the height from which it was released, and you get 3.80 meters