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Homework Help: Circular Motion - Spacecraft in Orbit

  1. Oct 28, 2011 #1
    The problem statement, all variables and given/known data

    A spacecraft moves in a circular orbit with a speed of 7.60E+0 km/s with a period of 95.1 min. What is the radius of the spacecraft's orbit?
    My answer, which is correct, is 6.90×106 m

    What is the radial acceleration of the satellite?
    8.37 m/s^2 was my answer, and it is correct.

    My issue begins right here:

    In order to begin its re-entry, the spacecraft engines are fired to provide an acceleration of 6.70 m/s2 in a direction opposite to its velocity. What is the magnitude of the spacecraft's total acceleration just after the engines begin to fire.

    The attempt at a solution

    The only thing I really grasp from this last question is that it starts going in the opposite direction, meaning you have to overcome the velocity it is originally going in to go the other way. Otherwise, I don't know where to start.
    Last edited: Oct 28, 2011
  2. jcsd
  3. Oct 28, 2011 #2


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    Science Advisor
    Homework Helper

    When the engine starts firing you have two accelerations acting on the craft. The radial from it's orbit and the tangential from the engines. I think the question wants you to add them as vectors and get the total magnitude.
  4. Oct 28, 2011 #3
    Thank you! I managed to get the answer. I appreciate the guidance.
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