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Why don't we feel the difference in Earth's angular velocity

  1. Jan 15, 2017 #1
    why dont we feel the difference in earths angular velocity between standing on north or south pole versus standing on the equator?
    Thank you
     
  2. jcsd
  3. Jan 15, 2017 #2

    Orodruin

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    The angular velocity (what angle the Earth turns per time unit) is the same at the poles as on the equator. Are you thinking of acceleration?
     
  4. Jan 15, 2017 #3

    Drakkith

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    The angular velocity is the same in both cases, so there is no difference. Are you asking why we can't feel the difference in the tangential velocity?
     
  5. Jan 15, 2017 #4
    That is what i meant Drakkith tangential velocity
     
  6. Jan 15, 2017 #5

    Orodruin

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    You can never feel a difference in velocity. You can only feel acceleration.
     
  7. Jan 15, 2017 #6
    things farther away from a center of axis cover larger distances than nearer objects within the same timeframe . farther away objects move faster, right?
     
  8. Jan 15, 2017 #7

    Orodruin

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    So what? You cannot feel velocity. You are currently moving at a velocity of ca 30 km/s relative to the Sun. Do you feel that? What distance is covered depends on which reference frame you consider.
     
  9. Jan 15, 2017 #8
    if we are in a car moving in circles. when we increase the velocity of the car, we would then feel that change in velocity as being pushed stronger away from the center of the circle!
     
  10. Jan 15, 2017 #9

    PeroK

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    How much different do you feel on an aeroplane, moving at 1,000 km/h, compared to a car at 100 km/h, compared to walking at 5 km/h?
     
  11. Jan 15, 2017 #10

    PeroK

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    If you are talking about that, how do you know it doesn't feel different at the poles from the equator? Maybe it does feel different?
     
  12. Jan 15, 2017 #11

    Orodruin

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    My emphasis.

    Exactly, but this is not due to the velocity, it is due to the acceleration, i.e., change in velocity.
     
  13. Jan 15, 2017 #12
    so my question is why dont i feel the change in velocity if i go on a direct flight from the pole to the equator.
     
  14. Jan 15, 2017 #13

    Orodruin

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    Because it is minuscule compared to the Earth's gravitational acceleration.
     
  15. Jan 15, 2017 #14
    thank you!
     
  16. Jan 15, 2017 #15

    PeroK

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    There's lots online about variations in the Earth's gravity for various reasons:

    https://en.wikipedia.org/wiki/Gravity_of_Earth

    Interesting fact of the day: if you tunnel down into the Earth, gravity increases for a bit! See the section on "Depth" on the above page.
     
  17. Jan 15, 2017 #16

    Drakkith

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    To expand a bit on Orodruin's answer, we need to take into account the fact that in a car the centripetal force on your body is provided by contact with the car itself. However, when dealing with the rotation of the Earth, it's gravity that is providing the centripetal force keeping you moving in a circle.

    The difference between the two is that the contact force between the car and your body only acts at the surface of your body on your skin. The force on all of your internal organs is transferred from your skin through the physical bonds making up your tissues and organs. Since your body is not a rigid object, things end up shifting around and compressing or stretching a bit depending on where they're located and what they're made up of. All this compression and shifting and such is what you're actually feeling.

    In contrast, gravity is not a contact force and can pull on ALL of your organs and tissues at the same time with approximately the same strength. Since there is almost no difference in the strength of gravity on any part of your body you cannot actually feel gravity by itself. An astronaut in orbit is actually in continuous free fall and cannot feel gravity pulling on them. It is only when gravity is opposed by another force, such as the normal force provided by the surface of the Earth, that you feel anything.

    The difference in the normal force at the equator and the normal force at the poles is very, very small. Far too small for you to tell the difference between the two.
     
  18. Jan 15, 2017 #17
    thank you!
     
  19. Jan 15, 2017 #18

    russ_watters

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    So, to expand on the answer to the question @mowi really intended to ask; the rotation of the Earth does impact the surface gravity -- or, rather, it causes the surface to not be perfectly spherical, which means that when you are on a pole, you are closer to Earth's center and thus the gravitational acceleration is higher than at the equator. In addition, the centrifugal force itself reduces your apparent weight on the equator. Further description and magnitude of the two effects (from PeroK's link):
    https://en.wikipedia.org/wiki/Gravity_of_Earth
     
  20. Jan 16, 2017 #19

    rbelli1

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    The difference in weight between the equator and the pole of an average adult is approximately the same as before and after emptying your bladder. Do you feel especially lighter after you pee?

    BoB
     
  21. Jan 17, 2017 #20
    The polar axis of the Earth is smaller than the equatorial radius. This makes people heavier at the poles than at the equator. The difference in radii in the Earth Ellipsoid is an even greater difference that the centrifugal force contribution to gravity.
     
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