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Will a jumper jumping out of a plane just drop from the spot he jumps from all what?

  1. Aug 26, 2011 #1
    my teacher said he will just drop from the spot he jumpe up from, not continue moving in the direction of the plane for a while. Is this the same when i drop a object i am holding out of the car window in a moving car?
     
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  3. Aug 26, 2011 #2

    Pengwuino

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    Re: Will a jumper jumping out of a plane just drop from the spot he jumps from all wh

    God I hope your teacher isn't a physics teacher. You will continue moving forward but will be slowed down due to the air resistance over time.

    Also, when you drop an item out of the car, it also travels forward as well, but again air resistance slows it down.
     
  4. Aug 26, 2011 #3

    tiny-tim

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    Just to add to what Pengwuino :smile: says …

    this is all about how we add velocities

    Vjumper,ground = Vjumper,plane + Vplane,ground

    see eg http://www.jfinternational.com/ph/problems-on-vectors.html" [Broken] :wink:
     
    Last edited by a moderator: May 5, 2017
  5. Aug 26, 2011 #4
    Re: Will a jumper jumping out of a plane just drop from the spot he jumps from all wh

    kay thx, so to confirm the kinetic enerygy doesent start from 0 when he starts to jumps off the plane right
     
  6. Aug 26, 2011 #5

    Pengwuino

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    Re: Will a jumper jumping out of a plane just drop from the spot he jumps from all wh

    Relative to the ground, no.
     
  7. Aug 26, 2011 #6

    HallsofIvy

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    Re: Will a jumper jumping out of a plane just drop from the spot he jumps from all wh

    Your teacher would certainly make a bad bombardier!

    (In defense of the teacher, who is not here to make his/her own defense, I have know students to tell me their teacher said such and such, to find later that the teacher asked if such and such were true in an attempt to get the students to think about it.)
     
  8. Aug 26, 2011 #7
    Re: Will a jumper jumping out of a plane just drop from the spot he jumps from all wh

    Well, if all you are interested in is how long it takes for the jumper to reach the ground, then even with (a separable form of) air resistance it will be irrelevant how fast the plane was moving, and it will take just as long for the jumper to reach the ground as if he had been jumping from a tower at the altitude of the plane. Also, (with no air resistance) the energy of the jumper is divided into a constant kinetic part along the "x" axis, and a constant kinetic/gravitational potential part along the "y" axis. Maybe that's what your teacher meant? I doubt that your teacher would have forgotten Newton's laws, but even so it sounds like he or she does a bad job conveying the subject accurately.
     
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