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Gravitational Field and free fall

  1. Aug 9, 2015 #1
    The acceleration of free fall at the equator is not equal to the acceleration of free fall at the poles.explain?
     
    Last edited by a moderator: Aug 9, 2015
  2. jcsd
  3. Aug 9, 2015 #2
    The main reason is centifugal force of spinning of earth. Besides, earth is not a perfect spheroid, it is a little flattened because of this centrifugal force.
     
    Last edited: Aug 9, 2015
  4. Aug 9, 2015 #3

    faiziqb12

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    i dont know what centrifugal force has to do with gravitation
    gravitation is just a matter of distance and mass
     
  5. Aug 9, 2015 #4

    A.T.

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  6. Aug 9, 2015 #5

    faiziqb12

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  7. Aug 9, 2015 #6

    HallsofIvy

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    The original post did not ask directly about "gravity", it asked about "the acceleration of free fall". That has to do both with gravitational force and with "centrifugal force" (actually the fact that part of that gravity goes to supply centripetal force keeping the object from flying off the rotating earth).
     
  8. Aug 9, 2015 #7
    If you are on surface on equator, I think that this is clear. Centrifugal force pushes you up. But if you are above the surface of equator and you are falling toward earth, you are also moving in the direction of rotation, but this means, that you are falling slower in comparison to nonrotating earth or on poles.
     
    Last edited: Aug 9, 2015
  9. Aug 9, 2015 #8

    A.T.

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    That's what this thread is about.
     
  10. Aug 9, 2015 #9
    But it is interesting if some meteoroid falls toward earth on equator. It falls like toward non-rotation earth, thus it does not feel earth's centrifugal force.

    Maybe this is what annoying you.
     
    Last edited: Aug 9, 2015
  11. Aug 9, 2015 #10

    faiziqb12

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    maybe centrifugal force effects gravitation on land and not in the sky
     
  12. Aug 9, 2015 #11
    This is not precisely. If you throw a stone from equator, its acceleration is smaller because of centrifugal force. Because rotation of earth is in-calculated in it.
     
  13. Aug 9, 2015 #12

    faiziqb12

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    i said maybe
     
  14. Aug 9, 2015 #13
    Thus, centrifugal force causes also on stone in the air (which flies from earth), but not on stone which flies from the universe.
     
  15. Aug 9, 2015 #14

    A.T.

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    Centrifugal force exist only in the rotating reference frame of the Earth, no matter if on land or in the sky. In the inertial frame there is no centrifugal force, no matter if on land or in the sky.

    https://en.wikipedia.org/wiki/Centrifugal_force
     
  16. Aug 9, 2015 #15

    faiziqb12

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  17. Aug 9, 2015 #16
    How do you explain that the gravitational acceleration is increased at the poles (compared to non rotating body) even though there is no centrifugal force?
     
  18. Aug 9, 2015 #17
    This looks a lot like an end of chapter question.
    It should be in homework section, shouldn't?
     
  19. Aug 9, 2015 #18

    faiziqb12

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    the gravitational force isnt affected at the poles by the centrifugal force{which is opposite in direction of gravitational force}...............
    so at the poles the gravitation is somewhat the same as it should be...
    but near the equator the centriful force plays its part so the gravitation gets decreased a little....
     
  20. Aug 10, 2015 #19

    A.T.

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    It's only opposite in direction exactly at the equator, not on the rest of the Earth. At the poles it's zero, so it's not opposite to anything.
     
  21. Aug 10, 2015 #20
    It is not the same as it would be without rotation.
     
  22. Aug 11, 2015 #21

    faiziqb12

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    i just said somewhat
     
  23. Aug 11, 2015 #22
    Then at the equator the gravitation is also "somewhat the same as it should be". At the poles the acceleration is 9.832 m/s² and at the equator 9.780 m/s². The centrifugal acceleration at the equator is 0.034 m/s² and therefore directly responsible for only 65% of the difference. That means there is an additional effect within the same order of magnitude.
     
  24. Aug 11, 2015 #23

    faiziqb12

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    somewhat always is used in contrast to another thing .................. for example here it was used in reference to gravity at equator........
    and yes i must commit that the gravity at the poles is actually that very much equal in magnitude to unaffected gravitation that the changes are negligible..........
    say me one thing is actually gravity is not 9.8 everywhere ...... then why we choosed it as a constant.............because changes are approx. negligible for us to take care of..........same is the case here
     
  25. Aug 11, 2015 #24
    That would be true if we wouldn't talk about the difference between the acceleration at the poles and at the equator. Compared to this difference the changes are not negligible.
     
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