Answer:
It takes the tennis ball approximately 0.78 seconds to reach the maximum height.
Explanation:
Use the formula for change in velocity equal the acceleration times the time, considering that the only acceleration acting is that of "g" (g = 9.8 m/s^2). Consider also that at the top of the trajectory is when the velocity becomes zero and the motion changes from upwards to downwards.
[tex]v_f-v_i=a\,*\,t\\0-7.6=-9.8\,*\,t\\t = 7.6/9.8\\t\approx 0.7755\,\,s[/tex]