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Homework Help: If a particle and a system have zero momentum

  1. Feb 25, 2008 #1

    DJW

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    Is it true that they both must also have zero kinetic energy?
     
  2. jcsd
  3. Feb 25, 2008 #2
    If we are talking of one particle, and it has zero momentum, it must have zero velocity (mass cannot be zero), and so its kinetic energy is zero.
    If a system of particles has zero momentum, any one particle in the system may still have momentum, say ,if it is vibrating in a lattice, but the system as a whole does not.
     
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