The vertical component of feet above the ground
h0 = 3 <--initial height
hF = 0 <--final height
90 mi/h = 90*(88/60) ft/s = 132 ft/s
v0 = 132sin(θ)
---------------------------------
The horizontal component of distance along the ground.
(Think of this as the shadow of the ball moving across the ground at
noontime with the sun directly overhead. The shadow moves along the
ground at a constant velocity.)
x0 = 0 <--initial distance along ground
xF = 300 <--final distance along ground
90 mi/h = 90*(88/60) ft/s = 132 ft/s <-- same as above
v = 132cos(θ)
-----------------------------
So we have this system of equations to solve:
Solve the second equation for t and substitute in the first
and get θ ≈ 16.08725911o <--answer
Substitute that back and get
t ≈ 2.36535260 seconds <-- you weren't asked for the time
I used a TI-84 calculator to get the answer
Round the answers as you were instructed.
I think your dad was on the right track, but the work is
so complicated, it's easy to make a mistake. Maybe I made
a mistake.
Edwin