Physics problem: how to do, thanks?

 x(t) = u cos(θ) t

y(t) = u sin(θ) t - 1/2 g t^2

x=30 at t=1,2 gives you the value of u cos(θ).

y=2.4 at t=1.2 gives you the value of u sin(θ).


u cos(θ) = 30m / 1.2s = 25 m/s

2.4m = u sin(θ) * 1.2s  - 1/2 *9.81m/s*2 * (1.2s)^2
u sin(θ) = 7.9m/s

Dividing the equations gives

tan(θ) = 7.9/25 => θ=17.5 degrees

u = 25m/s / cos(17.5) = 26.2 m/s