Question

Say you dropped a cannonball from the 17-meter mast of a ship sailing at 2 meters/second. How far from the base of the mast will the ball land?

Answer 1

Ask yourself - what is the relative horizontal velocity of the ball and the ship.

You have to assume that the mast is vertical (most sailing boat masts are NOT - even when the boat is stationary and becalmed)
You are not really concerned with vertical motion or acceleration here - just the movement of the ball away from the mast.
Beware, on top of all the assumptions, this is a sort of 'trick' question