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Where the ball will fall?

  1. Mar 16, 2007 #1
    1. The problem statement, all variables and given/known data
    If a person is sitting in a train which's starting from rest & he throws a ball upward,then where'll the ball fall?
    1)At the position where it's thrown?
    2)Behind the person?
    3) Ahead him?

    2. Relevant equations


    3. The attempt at a solution

    May be theory of relativity is involed,but not sure.
  2. jcsd
  3. Mar 16, 2007 #2
    All it involves are Newton's laws of motion.
  4. Mar 16, 2007 #3


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    Is the train accelerating at the moment when the ball is thrown ? Or in a state of steady motion ?
  5. Mar 16, 2007 #4
    The train is accelerating while the ball's thrown.Thanks for interest.
  6. Mar 16, 2007 #5
    What are the forces that act on the ball, along the horizontal direction, after it is thrown? (I suppose you can neglect any air-friction)
  7. Mar 16, 2007 #6
    No- I don't think you should neglect air-friction. It changes the choice from the list of possible answers.

    (Edit) Oh- I see the train is accelerating.

    (Of course, 'at the position where it's thrown' is meaningless under even gallilean relativity.)
    Last edited: Mar 16, 2007
  8. Mar 16, 2007 #7
    C'mon...this is most probably a question from intro-physics/mechanics; air-friction can always be neglected. :wink:
  9. Mar 17, 2007 #8


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    If the train accelerating when the ball is tossed, the ball will cease to accelerate when it leaves the throwers hand. The thrower will therefore move relative to the ball. All you need now is the direction.
  10. Mar 17, 2007 #9
    Air resistance can be neglected in intro to physics and some parts of mechanics courses.

    As far as relevancy to your question, the ball will move forward at whatever the velocity of the train is as it is accelerating. :zzz:

    You also need to understand, once he let go of the ball from his hand, it is no longer a part of the train so it is in a different dimension whilst the train is still accelerating.

  11. Mar 17, 2007 #10
    Is he on one of the seats facing forward? Or one of the seats facing backward? Last train I was on, the seats were arranged that way - facing each other.
  12. Mar 18, 2007 #11


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    Considering the phrasing of answers b and c 'behind him' vs. 'ahead of him', I would bet money that he's sitting in a forward-facing seat.
  13. Mar 20, 2007 #12
    Oh, I agree with that, but I think it's something that the question writer assumed without any thought. :)
  14. Mar 20, 2007 #13
    This is intro physics. Air has no resistance. Ever.
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