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Parabolic trajectory of a rocket

  1. Jan 6, 2009 #1
    Why is the trajectory of a rocket always parabolic if a rocket launches straight up in the air perpendicular to the ground? Doesn't a rocket just drop straight down back to the launch pad? I think the rocket lands away from the launch pad depending on the speed of the rocket.
     
  2. jcsd
  3. Jan 6, 2009 #2

    russ_watters

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    Staff: Mentor

    I would consider that to be a special case of a parabola or a limit condition. And it does drop straight down (ignoring the earth's rotation).
     
  4. Jan 7, 2009 #3
    Russ,

    What do you mean by limiting condition? So a rocket like an ICBM lands far away because of thrust vectoring?
     
  5. Jan 7, 2009 #4

    russ_watters

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    Staff: Mentor

    A limit condition is a simplified special case - like a circle is to an ellipse.

    And now I see your confusion - real rockets on launch pads tend to start off straight up. Yes, these rockets are steered. They don't end up on a ballistic (parabolic) trajectory until after their engines are stopped.
     
  6. Nov 21, 2009 #5
    If v of the rocket is high. But v < [tex]\sqrt{\frac{2GM}{R}}[/tex]
    where M is the mass of Earth
    R is the radius of Earth
    The trajectory of the rocket is a part of ellipse because g is change accordingly to h (likes the trajectory of planet). One focus of this ellipse is the center of earth.
     
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