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Homework Help: Quick question?

  1. Apr 18, 2009 #1
    Quick question??

    1. The problem statement, all variables and given/known data

    this is not really a problem just was wondering,
    does the following Kenimatics equation only work when the
    force is a constant or can i work when the F is changing?
    the equation is the one relating acceleration to velocity as follows

    V(final)^2 = V(inital)^2 + 2*a*d

    i know you can find a by using F=ma
    i used this problem a earlier to find final velocity of an orbiting planet.
    i used F to be equal to the graviational attraction between the two objects
    the whole

    G* m1*m2/r^2 thing.

    but not sure if that would work or not.
    if you know or have an opinion let me know
  2. jcsd
  3. Apr 18, 2009 #2
    Re: Quick question??

    Yes, that equation is derived under the assumption of constant acceleration, thus constant force.

    If you want to find equations of motion for non-constant acceleration, you must start with F=ma and use calculus to solve for the desired quantity.
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