A projectile is fired out of a cannon at 50 km/s, at an angle of 30 degrees and an elevation of 10m from the ground. How long does it take for the projectile to hit the ground?

Find the verticle velocity by resolving the velocity vector:

Trigonometry: 50sin30 = 25m/s in upwards direction

Using SUVAT for the vertical direction: S=-10, U=25, A=-9.81, V=N/A, T=?:

s=ut+0.5at² 
In the upwards direction: -10=25(t)+0.5(-9.81)(t²) 

0 = -4.905(t²) + 25(t) +10

Solve quadratic using x = (-b+/-SQRT(b²-4ac))/2a

t = 5.47 seconds as negative solution cannot exist