# How does Coriolis Force Work?

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How does Coriolis force work and how does it effect us on earth? What are some applications of Coriolis force?

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I will tell you right now, toilet flushing means nothing. That is largely affected with how toilets are made.

Imagine a spinning wheel, lifted off of the ground. The center of the wheel spins, but you’ll notice it isn’t moving anywhere. The outside of the wheel moves in circles, but the center doesn’t move anywhere.

This means the outside is moving faster than the center. The closer to the center you look, the slower it is moving.

If something were to travel from the center of the wheel to the edge, it would have to start moving faster to keep up with the part of the wheel it’s currently on. If it is sliding on a rail, then it will feel a force from the rail causing it to curve and pick up speed to match the wheel as it moves outward. This is the coriolis force.

If the object did not ride on rails and slid freely over the surface, following a true straight line, then as it moves outwards and the wheel moves faster beneath it, it draws a curved line on the wheel. This is the coriolis effect.

Its effects on Earth are only seen with very precise instruments, large systems, or fast systems. Bullets, airplanes, wind currents, and such.

If a wind blows towards the spinning axis of the Earth, so towards the nearest pole, the wind (following a ‘straight’ path) will appear to us on the surface of the wheel (the Earth) to curve eastward. Likewise if it blows towards the equator, it will appear to us on the ground to curve westward. This causes large wind systems (tornadoes, hurricanes) to form spinning one way in the northern hemisphere and the other way in the southern hemisphere.

It shows up in all scenarios where objects are spinning and moving, though, so the coriolis force is something that must be included when trying to model any spinning moving system. Engines, for instance.

Say you’re standing at the equator. Because the Earth rotates, you’re actually moving west to east at a little over 1000 mph. Everything near you is moving at the same speed, so you really don’t notice it.

Now your buddy is standing at 45° north latitude. *He’s* moving west to east at about 700 mph. Everything is moving together, so you both think you’re just standing still relative to each other.

You yell “hey, catch!” and whip a baseball straight to him. But by the time that baseball reaches his latitude, it’s still moving 1000 mph west-to-east, or about 300 mph faster than he’s moving. To both of you, it looks like the baseball inexplicably veered off to the east.

He says “you suck at this, let me show you how it’s done” and throws one straight to you. By the time it reaches your latitude, it’s going 300 mph slower than you are, and it seems that it veered to the west. You both go “wtf?”

That’s the Coriolis effect in a nutshell. Here’s what it does in real life:

Say you have a warm spot in the ocean. Warm air rises, and so the air at this warm spot rises, leaving a partial vacuum behind. Air from all directions flows in towards that spot. Air from the north veers west while air from the south veers east. So all this air that *ought* to have just flowed straight to the low pressure area winds up circling it instead.