You are a pirate being attacked by an enemy ship really really far away directly South of you. In which direction should you fire a cannonball from your ship to the enemy ship? Your Captain is skeptical and wants to fire directly south at the enemy ship. Use the Coriolis Effect to defend your aim to your Captain. (In the Atlantic ocean and in the northern hemisphere.)

You should aim slightly east of the enemy ship.

Explanation:

The enemy ship is closer to the equator.  Because the Earth is round, they have a higher velocity (like how a point on the rim of a spinning wheel moves faster than a point close to the center).

The Coriolis effect is basically just inertia.  It says that if you fire the cannonball directly south, that by the time it reaches the point where the enemy ship was, the enemy ship will have drifted with the Earth eastward.

To account for the difference in the speeds of the ships and the inertia of the cannonball, you must aim slightly eastward.