Assume you are a Medieval knight attacking a castle with a cannon. The ball leaves the cannon with a speed of 38.9 m/s. The barrel's angle with respect to the ground is 45.9°, and you make a perfect hit on the tyrant's chamber which is at the same level as the cannon's muzzle. What is the time of flight of the cannon ball?

In many of these types of problems the best approach is to separate the object's velocity into horizontal and vertical components. In this case you only need to deal with the vertical component of the cannon ball's flight. To get started - do you know how determine the initial velocity of the cannon ball in the vertical direction? Once you have that, you should be able to calculate how long it takes for the ball to reach its apex (hint: t = v/g), and then it will take that same amount of time again to fall from its apex back to its initial level.