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KE+PE when a rocket's speed is less than escape velocity?

  1. Jul 18, 2017 #1
    Hey people, I just want to ask that what will happen to the total mechanical force of the rocket if its speed is less than escape velocity?
    a. KE+PE=0
    b. KE+PE>0
    c. KE+PE<0
    d. Depends upon initial speed of the rocket
    Pick one. And Why??
     
  2. jcsd
  3. Jul 18, 2017 #2
    I guess C because at infinity we will have PE=0 and KE> 0 or equal to zero. As the rocket has not the tendency to move to infinity we conclude that
    PE+KE <0
     
  4. Jul 18, 2017 #3

    haruspex

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    I appreciate that it was a bit tricky with this one, but the rule on homework forums is to give hints and point out errors, not provide complete solutions.
    Correspondingly, @GrimReaper should have used the homework template and shown some attempt before meriting any help.
     
  5. Jul 18, 2017 #4
    I'm sorry if it was a mistake. And I'm totally new to this so I actually don't know how to use this. Thank you for the directions @haruspex.
     
  6. Jul 18, 2017 #5

    haruspex

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  7. Jul 18, 2017 #6
  8. Jul 18, 2017 #7
    Why is there no answer to this question? (Apart from the obvious fact that the question asks about force and gives answers in energy...)
     
  9. Jul 18, 2017 #8

    haruspex

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    The reference to force in the question statement is clearly an error. It should have said energy.
    The answer is given in post #2.
     
  10. Jul 19, 2017 #9
    oh sorry, actually its energy. I mistakenly typed force.
     
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