# The cause of aerospace rotation

1. Dec 1, 2014

### thegodof3d

Hi
What is the cause of aerospace rotation whit the earth?
May the gravity haves any roll?

2. Dec 1, 2014

### A.T.

You mean the atmosphere? Most of the atmosphere was formed rotating, like the rest of the Earth. And there is also friction resisting relative movement.

Also note that If it was always rotating with the Earth, then there would be no wind at all.

3. Dec 1, 2014

### thegodof3d

Thanks
I mean , if a body was suspensed on the air , may earth rotates and the body stayd , and if we jump and earth rotates and when we arrivrd on the ground we are in another place!

4. Dec 1, 2014

### A.T.

If there is no wind, the floating body will stay over the same point of the surface, obviously.

5. Dec 1, 2014

### Danger

Remember that you carry the angular momentum of the Earth with you during the jump. Think of the path that an object follows if you drop it "straight down" out of an aeroplane.

6. Dec 1, 2014

### DaveC426913

Or try jumping while on a train moving 60mph. When you jump, you don't drop from 60mph to 0. You carry the momentum with you that was imparted to you by the train.

7. Dec 1, 2014

### mmeftahpour

Dear friends, we have a discussion with thegodof3d. I say when you jump on the earth, we fall in different point because of earth rotation.
for small speed it is very small, but for larger amount it is considerable. I know we carry angular momentum when we jump, but our movement is not equal to earth movement. If we jump with 90 percent of escape speed, fall we again in the same point?
I think for small speed, we can consider gravity acceleration constant(9.8) and in vertical direction and also flat earth, these lead us to fall in the same point, but large speed means various gravity acceleration(depended to mass distance to center of earth , acceleration in central direction and round earth, so the equations are different.
I appreciate if you give your comment.

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8. Dec 1, 2014

### thegodof3d

Amazing!
You mean the primary speed of th earth thanks .
You mean the p

9. Dec 1, 2014

### DaveC426913

Well, yes. Where I live, the Earth is rotating at about 700mph about its centre. Because I'm attached to the Earth (as is everything around me), we are all rotating around the centre at that speed. If I jump up and down, I retain that speed.

This should not surprise you. It is exactly the same as jumping up and down on a train. Without looking out the window, you cannot tell you are travelling at 60mph wrt the ground. As far as you are concerned, you are stationary.

10. Dec 1, 2014

### mmeftahpour

Dear Dave
that's true for train, because the the train is Constant-Velocity, Non rotating Systems.
but I think it is not applicable for a system on the earth surface.(with variable velocity direction and also axis direction.

11. Dec 1, 2014

### CWatters

Are you referring to ..

http://en.wikipedia.org/wiki/Foucault_pendulum

That depends how high you "jump" and how accurately you measure distance. Normally when you jump in the air you land in roughly the same place.

12. Dec 1, 2014

### A.T.

It depends on how you jump. You can certainly jump in such a way, that you land on exactly the same spot.

If you jump just vertically, then Coriolis force will affect your path in the rotating frame of the Earth, and you won't land on exactly the same spot. Unless you are on one of the poles.

13. Dec 1, 2014

### Danger

That would be impossible to determine based upon a leg-powerd jump, though; the microscopic difference would be far overshadowed just by the fact that nobody can jump absolutely straight.

14. Dec 1, 2014

### mmeftahpour

yes, for human speed that's true and it is very very small, but in general view, for example if you shoot gun vertically, and bullet goes up 10 km. it fall in the same point? (consider there is no wind.)

15. Dec 1, 2014

### DaveC426913

The Earth is large enough that it can essentially be treated as an inertial frame of reference. It only changes by 15 minutes of arc every minute. You'd have to jump (or fall) from more than two miles to experience a quarter of a degree of rotation.

Last edited: Dec 1, 2014
16. Dec 1, 2014

### DaveC426913

So wait, you're going to ignore wind resistance? That's going to have an order of magnitude larger effect on your landing position than the rotation of the Earth. It's kind of the mathematical equivalent of "penny-wise, pound foolish".

This is beginning to sound like the old rotation-of-draining-water-in-a-toilet-bowl yarn. "OK, let's completely ignore all the macroscopic effects, and focus in the nanoscopic effects, and then claim the old wive's tale is true."

17. Dec 1, 2014

### mmeftahpour

Dear Dave
if we release a ball from tower with 400 m height there is 17 cm eastward deflection.(free fall in rotating earth - page 8)

18. Dec 1, 2014

### DaveC426913

19. Dec 1, 2014

### Staff: Mentor

Yes, there is a Coriolis effect on the earth. It is negligible in some cases but not in others.

20. Dec 2, 2014

### A.T.

For long range shooting Coriolis acceleration becomes relevant.

And even more so for long range
artillery:

Last edited: Dec 2, 2014