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Homework Help: Rocket Conservation of Moment

  1. Oct 16, 2013 #1


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    I really need clarification for this problem.

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

    A rocket with initial mass M0 is accelerated by expulsion of a partial mass dm of its mass m with a constant velocity u. Write down the differential equation corresponding to the conservation law of momentum for the velocity v(m) of the rocket and evaluate it under the condition v(m = M0) = v0. What is the terminal velocity when the final mass of the rocket is Me?

    3. The attempt at a solution

    I have attached three different approaches (all using the conservation of momentum principle) of mine in this pdf file.
    But unfortunately I get three different results.
    Please point out which approach is wrong.

    thanks a lot

    Attached Files:

  2. jcsd
  3. Oct 16, 2013 #2


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    Homework Helper

    What are your thoughts about the three methods? I think you can apply some physics insight to decide which is correct.
  4. Oct 16, 2013 #3


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    I really can't tell. All three methods appear to be correct to me. I can't see what is wrong about any of the methods. But obviously because I get different answers something has to be incorrect, but I just can't tell what.
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