# Homework Help: Rotation of earth and wind

1. Aug 7, 2016

### Vibhor

1. The problem statement, all variables and given/known data

Ans : b)

2. Relevant equations

3. The attempt at a solution

Assuming wind mass moves towards east at the equator , as it moves up it retains its linear speed . At higher latitudes the angular speed of earth is same but linear speed at the surface of earth decreases . So , wind mass shifts towards east relative to surface of earth .

The thing I would like to understand in this question is that - how does rotation of earth from west to east at the equator imparts an eastwards velocity to the wind mass ?

I might be missing something very simple .

Thanks

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2. Aug 7, 2016

### haruspex

It could be made clearer, but the initial northwards movement stated is supposed to be relative to the Earth's surface.

3. Aug 7, 2016

### Vibhor

Ok . But any thoughts why wind is also moving from west to east close to earth's surface ?

4. Aug 7, 2016

### haruspex

If the Earth's surface is moving West to East, and the air is moving North relative to that, then necessarily the air has an eastward component in absolute terms.

5. Aug 7, 2016

### Vibhor

I agree . Logically you sound right . But what I am asking is whether rotation of earth influences rotation of wind such that they both rotate towards east . Is there some sort of friction involved between earth and lower layers of wind which make wind rotate ??

Any simple reasoning you can think ?

6. Aug 7, 2016

### ehild

The
The atmosphere belongs to the Earth. You can think that Earth formed from a rotating cluster of particles, the denser and bigger ones made the inner part of the Earth and the gaseous part formed the atmosphere. So the atmosphere rotates with the Earth. And yes, there is kind of friction between the surface and the air moving relative to it, and there are viscous forces between moving parts of air.
If the wind blows to North, the velocity of the air in the wind has both Northward and Eastward components for an observer in an inertial frame of reference outside the Earth. The Eastward component is the same initially as the linear velocity of the Equator.

7. Aug 7, 2016

Nice !

Thank you .

8. Aug 7, 2016

### haruspex

As ehild says, yes there is. To complete the picture, when, as must happen, an air mass moves towards the equator it finds itself lagging, so bends to the West, relative the Earth. The friction gradually brings it up to the eastward speed for the new latitude.

9. Aug 7, 2016

Thanks