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Homework Help: Projectile Motion, Shooting a Ball in Zero Gravity. !

  1. Jan 25, 2010 #1
    Projectile Motion, Shooting a Ball in Zero Gravity. URGENT!

    So I had to come up with my own problem for class, but this is going to be in zero gravity. I chose lacrosse.

    1. The problem statement, all variables and given/known data
    Chris Fiore does a split dodge with the help of a pick and gets his hands free for a sidearm shot from 15 yards. He is so good that when he shoots, the ball always travels in a 2D path! The initial velocity of the shot is 96mi/h (Chris Fiore is one of the fastest shooters in lacrosse). How long does it take until it hits the goal?

    2. Relevant equations
    Conversions:
    15yd (0.91m) = 13.72m
    96mi/h(1609.34m)(3600s) = 5.56x108m/s

    d = vit + 1/2gt2

    3. The attempt at a solution
    If this is how it is calculated on Earth...
    d = vit + 1/2gt2
    13.72 = (5.56x108)t + 0.5(-9.81) t2
    -4.91t2 + 5.56x108x -13.72 = 0
    t = 2.47s

    What the hell happens if the gravity is zero? I can't just put in 0 instead of -9.81 can I? From what I recall the whole formula doesn't even work if its not on earth! The ball would go insanely fast! Need some clarification on this. How would I go about calculating this? Thanks!
     
    Last edited: Jan 25, 2010
  2. jcsd
  3. Jan 26, 2010 #2
    Re: Projectile Motion, Shooting a Ball in Zero Gravity. URGENT!

    Hi there,

    Without the gravity field, you object will not fall. It will simply travel at constant velocity (neglecting the air friction) until it hits the goal!!!
     
  4. Jan 26, 2010 #3

    Matterwave

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    Science Advisor
    Gold Member

    Re: Projectile Motion, Shooting a Ball in Zero Gravity. URGENT!

    Are you sure about that 5.56x10^8m/s speed of the ball? This Chris Fiore guy must have one hell of an arm to be able to shoot that ball faster than the speed of light!
     
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