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Mass and velocity

  1. Jun 24, 2013 #1
    Why does a particle gain mass/momentum as its velocity increases?

    How does this happen?
    Last edited: Jun 24, 2013
  2. jcsd
  3. Jun 24, 2013 #2


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    Staff: Mentor

    Ignore the previous reply, it was wrong and crackpottery and got deleted accordingly.

    It does not gain mass. It gains momentum as momentum is defined as a velocity-dependent quantity (in classical physics, just mass*velocity).
  4. Jun 26, 2013 #3
    Ahhh thanks
  5. Jun 27, 2013 #4
    You must be referring to relativistic mass. The change in mass with speed is due to the combination of length contraction and time dilation, i.e. due to the properties of spacetime.
  6. Jun 27, 2013 #5
    Momentum is directly proportional to mass of object as well as the velocity,

    And thats why mass doesnt change but the velocity in your case may be constant or relative!

    Thats actually the definition of momentum too.

    As mfb said it doesnt gain mass but momentum.
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