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Will an object moving at a constant motion

  1. Oct 17, 2004 #1
    If an object moving at a constant speed be launched into orbit? Irregardless of what that speed is and time not being a factor.
  2. jcsd
  3. Oct 17, 2004 #2
    A constant speed requires a constant force to push the object. However, gravity is pulling the object down at a constant acceleration of 9.8m/s^2, and of course air resistance.

    The minimum speed to get an object out of the Earth's atmosphere is around 11km/s, according to 0.5mv^2 = GmM/R.
  4. Oct 17, 2004 #3
    Actually, since the force of gravity is inversely proportional to the distance r between the center of the earth and the object, and since the density of the atmosphere also decreases as the distance from earth increases, a decreasing force will propel an object at a constant speed.

    That's the speed an object must have at (or very close to) the surface of the earth in order to escape earth's gravitational pull, assuming that no force other than gravity (i.e. no air resistance, no propulsion) acts on the object after it has reached that speed.

    If an object moves at constant speed, meaning that it has some means of self-propulsion, it will not go into orbit. It will just keep moving further and further away from the earth.
  5. Oct 17, 2004 #4


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    Depends on the aerodyamic drag that occurs until the object gets past the atmosphere, but yes, if the initial speed is high enough, then the object will go into orbit (assuming it doesn't burn up while traveling through the atmosphere).
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