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How does the Coriolis Effect work?

In most cases, the object is moving with the earth. When the object is released, it keeps its horizontal motion, staying above the target. The object maintaining this motion even when no longer in contact with what was holding it is inertia. An object will not stop moving unless forced to. Also, an object will not start moving unless forced to.

One example that clearly shows inertia is the pouring of coffee on a jet plane. The plane is traveling at hundreds of miles per hour, as is the coffee cup, coffee pot, and coffee itself. When the flight attendant pours the coffee, it does not shoot toward the back of the plane at hundreds of miles per hour. The coffee moves downward into the cup below. The coffee continues moving forward with the plane, keeping in line with the cup, even after leaving the pot.


Melissa -

It might be easiest to think of the motion on the surface of the earth as being on a tangent line rather than a circle. In reality, the arc is so great that this is not too far off.

Thinking this way, the surface of the earth and the object being dropped are in the same inertial plane. They have the same motion along the tangent. Even though an object is dropped vertically, this does not affect its motion along the tangent. The object would continue to move just as the surface of the earth below it.

Try it out. Sit in the back seat of a car and drop something from the ceiling. It will fall straight down as compared to the car (a metaphor for the earth).

I have been asked this same question numerous times. It has come from deep thinking people. Keep thinking.

Larry Krengel

No, because everything on earth is spinning, and everything is affected by gravity -- all the same. It is just like riding in a car. If you are holding a ball, lets say, and you drop it in a moving car, the ball will fall straight down.

Katie Page

If the object is spinning with the earth then you can ignore the rotation (they are both moving together so there is no relative motion about the axis of rotation). If, however, an incoming alien (not in geosynchronous orbit) wanted to drop a package down to a friend on the surface he/she/it would have to take into account the relative motion of the planet and their space vehicle.


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