Answer:
19.6 m
Step-by-step explanation:
The total motion of the golf ball lasts 4.0 seconds: since the motion is symmetrical, it takes 2.0 s for the ball to reach the highest point and then another 2.0 s to land back on the tee.
Therefore, we can just analyze the second half of the motion that lasts
t = 2.0 s
During this time, the vertical distance covered by the ball is given by the equation:

where
u = 0 is the initial velocity (zero because the ball starts from its highest point, where the velocity is zero)
t = 2.0 s
g = 9.8 m/s^2 is the acceleration of gravity
Solving for d, we find:

So, the ball reaches a maximum height of 19.6 m.