Question About Mass

Discussion in 'Physics & Math' started by OilIsMastery, Nov 30, 2008.

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  1. BenTheMan

    BenTheMan Dr. of Physics, Prof. of Love Valued Senior Member

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    That much is obvious. I doubt that you come here in good faith, but I will explain to you why you're wrong, nonetheless.

    p = mv is the definition of momentum for something with mass. When the something doesn't have mass, like a photon, this definition of momentum is not valid. Physicists didn't "rewrite" anything, we had to come up with new forumlae to describe what it was we were observing.

    For a photon, the momentum is defined as p = hf/c, as I said before. h and c are constants of Nature, and f is the frequency of the light.

    The law of conservation of momentum is \(\sum\vec{p}_i + \sum\vec{p}_f = 0\). That is, the momentum before a collision and the momentum after a collision sum to zero.
     
    BenTheMan, Nov 30, 2008
    #21

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  3. OilIsMastery

    OilIsMastery Banned Banned

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    In what way is a question wrong?

    How do we know a photon has no mass?
     
    OilIsMastery, Nov 30, 2008
    #22

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  5. BenTheMan

    BenTheMan Dr. of Physics, Prof. of Love Valued Senior Member

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    You already know what the answer is. You have things already figured out in your head, and you know that the rest of the world is wrong, and that you're right. That's cool, man, really---but don't expect me to tolerate much of your bullshit here.
     
    BenTheMan, Nov 30, 2008
    #23

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  7. OilIsMastery

    OilIsMastery Banned Banned

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    You are wrong and you are trolling.
     
    OilIsMastery, Nov 30, 2008
    #24
  8. BenTheMan

    BenTheMan Dr. of Physics, Prof. of Love Valued Senior Member

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    So, I see you're done talking about physics.
     
    BenTheMan, Nov 30, 2008
    #25
  9. OilIsMastery

    OilIsMastery Banned Banned

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    No. I asked questions about physics and you are trying to make this personal.

    I ask again, how do we know a photon has no mass?
     
    OilIsMastery, Nov 30, 2008
    #26
  10. Trippy

    Trippy ALEA IACTA EST Staff Member

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    Actually,m it completely answers the question, you just apparently lack the skills to recognize as such.
     
    Trippy, Nov 30, 2008
    #27
  11. OilIsMastery

    OilIsMastery Banned Banned

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    Trippy, just so you know here are the questions you haven't answered:

    (1) Is it possible for something with no mass to move something that has mass?

    (2) Why did physicists rewrite p=mv for photons?

    (3) How do we know a photon has no mass?
     
    OilIsMastery, Nov 30, 2008
    #28
  12. BenTheMan

    BenTheMan Dr. of Physics, Prof. of Love Valued Senior Member

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    Thread locked.

    Question has been answered.
     
    BenTheMan, Nov 30, 2008
    #29
  13. James R

    James R Just this guy, you know? Staff Member

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    Yes. Example: photons have no rest mass, yet can exert forces on massive particles.

    Because p=mv was found to be a non-relativistic approximation.

    Because only zero-mass particles can travel at the speed of light.
     
    James R, Dec 1, 2008
    #30
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