[ot][spam][crazy][crazy][spam]

[Karl Semich]

simulate to test.

p_y(t) = 0 + vy * t - g t^2 / 2
p_x(t) = 0 + vx * t

t_f = vy / g
v_x = p_x(t_f) / t_f = p_x(t_f) * g / vy