Beginner Projectile Motion problem

[Myll]

Homework Statement

Fire a cannon ball at 30 degrees above the horizontal with an initial speed of 65 m/s from the top of a building 50 m high.

Find the total time the cannon ball is in the air.

What's the horizontal distance from the base of the building when the ball strikes the ground?

Homework Equations

The Attempt at a Solution

For the time I got 7.9 s, but I don't know if that's right.

 

[lewando]

How did you arrive at that result?