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Mechincal Energy

  1. Jun 19, 2011 #1
    1. The total mechanical energy of a system:

    a. is split equally between kinetic energy and gravitational potential energy.
    b. is constant as long as only conservative forces act on it.
    c. is either only kinetic energy or only gravitational potential energy at any given time.
    d. cannot be determined for most naturally occurring systems.

    For this question, I think the answer is A. This is because Total Mechanical Energy is eqaul to Potential Energy + Kinetic Energy. Is my reasoning right?
     
  2. jcsd
  3. Jun 19, 2011 #2

    gneill

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    Staff: Mentor

    So, you're proposing that KE is always equal to PE?
     
  4. Jun 19, 2011 #3
    Yes..isnt that right?
     
  5. Jun 19, 2011 #4

    gneill

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    Staff: Mentor

    In all the projectile problems that you've worked on, was potential energy always (at all times) equal to kinetic energy? Even, for example, when a vertically launched projectile is at the top of its trajectory?
     
  6. Jun 19, 2011 #5
    Oh no it wasnt the same. So since its not split equally, it would be C then?
     
  7. Jun 19, 2011 #6

    gneill

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    Staff: Mentor

    I think that you should reflect on the problems that you've done involving PE and KE and try to draw logical arguments for accepting or rejecting the provided choices. Remember, a single counterexample disproves a proposition.

    I'm not going to answer your question for you by eliminating or confirming them one at a time when you say something like, "Is it C?" :smile:
     
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