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Bullet speed

  1. Nov 18, 2007 #1
    Does a bullet speed up after leaving the gun?
     
  2. jcsd
  3. Nov 18, 2007 #2

    LURCH

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    Science Advisor

    If it's fired downhill in a vacuum, yes. Otherwise, no.
     
  4. Nov 18, 2007 #3

    russ_watters

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    Staff: Mentor

    We got this exact question a month or so ago - where is this coming from, Charles?
     
  5. Nov 18, 2007 #4
    I was driving my van the other day and i noticed that when i pressed the clutch in to change to second gear the van seemed to continue accelerrate, with nothing powering it, just for maybe 1 second(or perhaps i imagined it).

    That got me thinking about other things like bullets. Also does a cricket ball accelerate away from the bat with nothing pushing it, surely it can't get to it's return speed instantly.
     
  6. Nov 18, 2007 #5

    rcgldr

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    In the case of a gun, there's still some pressure just as the bullet leaves the barrel, but this is a very short distance.

    Once a ball leaves a bat, golf club, ... it no longer accelerates, and starts decelerating because of drag immediately.

    In the case of a van, the suspension relaxing after acceleration mave give a rider a sense of continued acceleration, but the center of mass isn't accelerating. Sometimes the lack of deceleration force felt when braking then releasing the brakes, and car body pitch can give a false sense of acceleration as well.
     
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