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Old Jul 6th 2010, 02:49 PM   #1
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The famous flight to east VS flight west, can someone give a clear explanation

The answer to the "classic" question whatever flying from west to east is faster then flying from east to west, is one of the most tricky debates I saw in physics... usually people answer that the reason is that earth is rotating and coming to you.
(which is wrong...)

The answer is the jet stream.

all nice.

But the question is why not, I tried to find a clear explanation of it, and could not, if for example I take off from JFK and start moving in the opposite earth rotation what is the force/rule/wind/gravity/roation.. that keeps me in the same relative speed as earth all the time?

Last edited by Hbar; Jul 6th 2010 at 03:28 PM.
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Old Jul 6th 2010, 09:22 PM   #2
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I think the explanation of the Earth's rotation is sort of incomplete explanation. Actually during the flight the motion of plane is independent of rotation of the Earth if air is not present. When air is present, the surface of the Earth will drag the air to rotate in the same sense of the Earth. By then, the drag force will cause the slowing down of the plane.
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Old Jul 13th 2010, 02:32 PM   #3
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mmm not sure..

After all if even air isn't present, still when you leave a rotating sphere (or disc .. doesn't matter..) you first gain it's initial speed (in our case the speed of earth spin, so even if air isn't present still the plane will have an initial speed of earth (which is very high, and no plane motor can overcome it..).
It;s like throwing a small ball in a moving car, and let's say the ball have small motor which can move the ball (in the opposite direction ) once it leave the hand, but let's say the motor is very weak or very small compare to the initial ball speed so the ball movement will still be an arc.
of some sort.

This same phenomena happen here, in some way but I am not sure..
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Old Jul 14th 2010, 06:48 AM   #4
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Here's an analogous sitiuation - suppose you are riding on a train going 60 MPH. You and a friend start tossing a ball back and forth, and you throw at a speed (relative to you) of 30 MPH. Does the ball actually go at 60-30 = 30 MPH when thrown forward, and 60+30 = 90 MPH when thrown toward the rear? Depends on your point of view. To an observer on the ground - yes, but to an observer on the train - no, the ball always goes at 30 MPH.

Same thing with the plane flying west-to-east versus east-to-west. To an observer in space the plane does indeed appear to travel faster when going west-to-east. But to an observer on the earth (which is rotating west-to-east at a speed of near 1000 MPH) the airplane's speed is the same regardless of which direction it is flying. So as long as we are located at the surface of the earth it doesn't matter which way the plane flies.

This ignores the fact that the prevailing winds are usually west-to-east, so in fact planes do fly marginally faster when heading to the east -- but no where near the 2000 MPH difference that would be attributable to the earth's rotation.

Last edited by ChipB; Jul 14th 2010 at 07:38 AM.
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Old Jul 14th 2010, 07:17 AM   #5
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In that case let's say the following,
If I have a ball that can levitate in place for an hour, and I will put it in the mid air in the train and wait (now he is no longer in the train system, although it get the train initial velocity.. ), will it or will it not, bounce in the end of the wagon wall after few min?

If the answer to that is no, it will stay in place..
Then ask yourself what will happen if I will reach out and put the same ball outside the window of the wagon, and wait, surely after an hour he will stay alone on the track as the train will pass him.. (depends on the length of the train of course..)

So what it will be??
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Old Jul 14th 2010, 07:33 AM   #6
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Originally Posted by Hbar View Post
In that case let's say the following,
If I have a ball that can levitate in place for an hour, and I will put it in the mid air in the train and wait (now he is no longer in the train system, although it get the train initial velocity.. ), will it or will it not, bounce in the end of the wagon wall after few min?

If the answer to that is no, it will stay in place..
Correct. Ever been on an airplane flying at close to 600 MPH, with a fly buzzing around the cabin? It doesn't get smushed against the rear of the cabin, for the same reason.

Originally Posted by Hbar View Post
Then ask yourself what will happen if I will reach out and put the same ball outside the window of the wagon, and wait, surely after an hour he will stay alone on the track as the train will pass him.. (depends on the length of the train of course..)

So what it will be??
The levitating ball will actually continue to move at the same speed as the train and keep pace with you, EXCEPT for the fact that wind resistance acts to slow it down. Nothing confusing about that. If you did this same experiment on the moon, where there is no air to create resistance, the levitating ball would not slow down relative to you.
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Old Jul 14th 2010, 07:36 AM   #7
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OK. make sense, the initial speed will stay the same since there is no drag or force to make it go slow.

So in the case of the airplane it is the same thing.
nice.
(except the winds effect.)
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