Question 834573
given:
h = -16t^2 + 104t
.
The "initial" point of departure is when 'h' is zero.  So, set h to zero and solve for t:
0 = -16t^2 + 104t
0 = 4t(-4t + 26)
t = {0,13/2}
answer:
t = 13/2 seconds
or
t = 6.5 seconds