Here's how I did it:
Distance = d
Gravity = g
Tank's Acceleration = a
You know that the vertical speed (
Vv) is equal to the velocity (
V) times the sin of theta (
@).
Vv = V * sin @
The horizontal speed of the shell (
Vh) is equal to
V * cos @.
Vh = V * cos @
At the midpoint in time
Vv is
0 (it is at the apex), so you can enter
0 for Vfinal in the equation Vfinal = Vinitial + acceleration * time.
0 = (V*sin @) + g*t
When you solve for
t you get
t = (-V*sin @)/g.
Double this to get the total time (time of ascent + time of descent).
t = (-2V*sin @)/g
The horizontal distance can be found by entering the values for
Vh and
t.
d = (V*cos @)*((-2V*sin @)/g)
This is equal to the distance the tank travels, which can be found using the equation
d =(1/2)a*(t^2)
Since the distances are equal, you can create the following equation:
(V*cos @)*((-2V*sin @)/g) = (1/2)a*(t^2)
When I solved for
@ I got
@ = tan^(-1) (-g/a)
I apologize if this is wrong, but I really don't think it is.

Now I need to get to bed so I can take
my physics test tomorrow.
