Questions on classical mechanics

  1. Apr 8, 2013 #1
    Question 1
    i was wondering if there is any method to find the point from which the angular momentum is a conserved quantity. let me e.g. choose the case of a planet moving in an orbit around the sun. In this case, the angular momentum measured from the center of mass as the point of reference is conserved. But if i choose a different point, that is not exactly on the line connecting the planet and the sun, then the angular momentum is varying with time. so how do i found out how to choose this point, if the system is more complex?

    Question 2
    if F is a conservative force field, then the energy is conserved. is the converse, the energy is conserved, therefore we have a conservative force field also true?
  2. jcsd
  3. Apr 9, 2013 #2

    Simon Bridge

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    To be more precise: the sun and the planet each orbit their common center of mass.
    But it is still conserved.
    You mean you want to find a reference frame in which a particular bodies angular momentum is a constant?

    Is it not always the center of mass for gravitating systems?

    Kinetic energy is conserved in an elastic collision: is the collision an example of a conservative force field?
  4. Apr 9, 2013 #3
    Thank you for your answer, but is this a question or an answer?
  5. Apr 9, 2013 #4

    Simon Bridge

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    That's up to you :) Both - I hope.

    It can be hard to tell if a statement followed by a question mark is an actual question or a rhetorical question.
    All the questions in post #2 can be safely treated as actual questions. I am posing them as a way to help you clarify your thinking and so find the answers you seek.
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