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Earth rotation

  1. Mar 16, 2015 #1
    if we fly over a moving train at the speed of train can we out run it?? it not, how come we fly at 255m/s when earth is rotating at 460m/s and we reach from paris to america
     
  2. jcsd
  3. Mar 16, 2015 #2

    Drakkith

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    Staff: Mentor

    The plane is moving at 255 m/s relative to the surface of the Earth. An observer not rotating with the Earth would see the plane as flying at 715 m/s if it is traveling east or 205 m/s if it is traveling west.
     
  4. Mar 16, 2015 #3
    Dear drakkith,

    earth rotation as i understand, means india will move relative to atomosphere from point a to point b at 1656km/hr. in the same atmosphere a plane start from india at 920km/hr west ward. how it reachs lets say africa when plane is at half the speed of earth.
     
  5. Mar 16, 2015 #4
    India or anywhere else is NOT moving relative to the atmosphere.
    The Earth's atmosphere rotates along with the Earth's surface, at the same speed, more or or less.
    Small local differences are what we call 'wind'.

    A plane in the atmosphere is therefore also rotating along with the the rotation of the planet,
    and in addition to that the plane also has a given air speed and direction.

    A plane flying at 1000kph either east or west or in any direction will travel 1000km in one hour RELATIVE TO THE EARTH'S SURFACE.
    We don't calculate the speed of the plane relatively to some fixed point in space outside of the Earth because that has no practical value whatever.
     
  6. Mar 16, 2015 #5
    On a somewhat related topic - what exactly are the physics that allow an aircraft to cover large distances in shorter times the higher they go (proposed sub orbital flights)

    Is it because at those heights they are escaping some of the atmosphere? Or is it the higher one gets the greater his (or her) speed relative to the surface below is?
     
  7. Mar 16, 2015 #6
    Your first guess is correct.
    The atmosphere at a typical cruising altitude for a jet is very much thinner than it is at sea level.
    The aircraft therefore experiences much less 'drag' (air friction basically) and so it is effectively able to travel further with a given amount of fuel.

    A 'sub-orbital' flight would probably still encounter a small amount of very thin air, but yes it would in principal be even more fuel efficient.
    However such an aircraft could not use regular turbine engines where there is so little air, it would need to use rockets or some kind of ramjet, which I imagine would be less efficient in use of fuel than a turbine
     
    Last edited: Mar 16, 2015
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