Coriolis Effect Lecture

" I didn't get what I wanted for Christmas so I spent the last few months (I teach this in March-ish) formulating a plan and finally carried it out this weekend. I spent my weekends making a super snowball cannon, when it was finally finished I set it up. Now since I am not a Math teacher, I wanted to make the mathwork as simple as possible so I made my calculations for the equator. I brought my super snowball cannon to the equator along with a perfectly spherical snowball laced with radioactive tracking dye so I can monitor it's progress once launched.

I aimed the cannon directly at the evil little Elf's belly button and fired WHOOOSH! It took exactly one hour to reach the north pole, but one thing I failed to take into account is that the Earth is rotating- and at the equator the Earth is moving at about 1,000 miles per hour. The Snowball impacted directly in front of the cannon, which after an hour travel time was 1,000 miles to the right of the North Pole (a spot I mark out in space next to the pole). The radioactive tracking dye allowed me to track it and here's it's path. (I draw the traditional Equator-to-Pole path curving right and impacting at the spot in space).

Santa, seeing this blatant attack, and being the vendictive elf that he is, takes out his own, already-made, supersnowball cannon. Exactly 24 hours later, I swing around into his sights. He aims and fires WHOOOSH! He thinks he has no problem hitting me since he is not moving and will not have the same side-stepping slip that I did. But in the hour that it took his snowball to reach the equator, I have moved to the East 1000 miles and the snowball splashed harmlessly behind me. If I reset the map to when he fired, the snowball impacts here (1000 miles to the left) and follows a path like this (from North Pole to Eq curving to the left- as seen from the class)"

I then take out a large toy car and slowly drive it up the board along my first path while asking "which direction is the driver turning?"


Then I drive the car from the Pole to the Equator. "Now which way is the DRIVER turning his wheel?"

To the right

I don't discuss trajectories along latitude lines but I use these two examples to derive the rule: objects in the northern hemisphere turn to THEIR right. I then draw lines radiating from a center and curving, pinwheel-style outward and to the right. (I just avoid doing 4 arrows since it looks like a swastika!)

See the Youtube Video