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Homework Help: Kinetic Energy and Momentum

  1. Nov 21, 2004 #1
    This is a question from a practice test, so it might also be a test question. For some reason I am tripping myself up on it:

    A space vehicle mas m has a speed v. At some instant, it separates into two pieces each of mass 0.5m. One of the pieces is at rest just after the separation.
    (A) Does this process:
    (a)conserve kinetic enery (b)not conserve total enery (c) the moving piece has a speed 2v (d) not conserve momentum

    (B)what is the KE of the moving piece just after the separation:
    (C) how much work was done by the internal forces that caused the separation:

    For part B and C the multiple choice answers are the same
    (a.) 0 J (b). 1/4mv^2 (c.)1/2mv^2 (d.) mv^2 (e.) 2mv^2

    Any help on this, my first thought were that (A) the speed is 2v (B) 2mv^2 (C) ? not sure
  2. jcsd
  3. Nov 21, 2004 #2
    Think about this: which is a vector quantity, energy or momentum?
  4. Nov 21, 2004 #3
    Consider that piece that now has the velocity 2v what was its initial velocity

    using the work -energy theorem,

    [tex] W = \Delta K [/tex]

    that your answer for C

    your answers for A and B are fine
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