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Homework Help: How would gravity act on an object with no velocity?

  1. Jun 19, 2013 #1
    1. The problem statement, all variables and given/known data

    Suppose there was a planet in deep space. Now drop an object in it's gravitational field. This object has no velocity whatsoever in any direction. Now, would this object start moving straight toward the planet (because that's the direction of net force) or follow a circular pathway (because gravity is a centripetal force). Please explain why?

    2. Relevant equations

    3. The attempt at a solution

    My intuition tells me that this object would follow a circular pathway. But I have no way to rationalizing why.
  2. jcsd
  3. Jun 19, 2013 #2

    Simon Bridge

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    You need to revisit you circular motion physics - can you have a curved path without any initial tangential velocity?
  4. Jun 19, 2013 #3


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    I have no idea why your "intuition" would say such a thing! The gravitational force on an object acts directly toward the center of the planet. The same thing will happen to this object that would happen to a rock when you dropped it- it will move straight "down" toward the surface.

    If the planet is rotating, the point at which the object hits the surface will not be the point that was directly beneath the object when it started falling but that is due to the rotation of the planet, not the motion of the object.
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