Why photon is mass-less?

Discussion in 'Physics & Math' started by Saint, Feb 9, 2020.

  1. exchemist Valued Senior Member

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    You are NOT a lecturer who teaches dynamics.

    Do not tell such obvious lies.

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  3. Saint Valued Senior Member

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    I study Mechanical Engineering, Dynamics is a compulsory subject.
    If I push a wall with force and the wall does not move, I did NO WORK, because F(0) = 0.
    But I feel exhausted, where did my energy go?
     
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  5. exchemist Valued Senior Member

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    It's because of the way muscles exert force. They do this by a biochemical process that continuously consumes chemical energy (appearing finally as heat) while the muscle fibres are in tension.

    The process is complicated: look up sliding element theory, for example, if you want to read about how it works. I am not an expert on this.

    But you are now hijacking your own thread onto a totally different subject.
     
    Last edited: Feb 14, 2020 at 8:28 AM
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  7. James R Just this guy, you know? Staff Member

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    They didn't cover this in your compulsory subject? That's unfortunate.

    You did no external work on the wall because the wall didn't move. However, some internal transformations of energy occurred within your body. Some chemical energy in your muscles was transformed into internal kinetic energy of the muscle fibres and into waste heat. There are many other internal energy transfers that occurred as you pushed against the wall.

    When you talk about work, you need to be clear about what system you're considering. Here, it seems that you were considering the system that consists of your entire body, and its potential to do work on the outside environment (which includes the wall). If you were to define a different system, you might be able to reclassify some of the internal energy transfers as work, because those energy transfers would no longer necessarily be internal processes.
     
  8. James R Just this guy, you know? Staff Member

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    What do you lecture, and to whom do you lecture?
     
  9. Saint Valued Senior Member

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    Mechanics of Solid.
     
  10. (Q) Encephaloid Martini Valued Senior Member

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    Just curious, do you happen to lecture at MIT?
     
  11. James R Just this guy, you know? Staff Member

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    At university level?

    Which department and faculty are you in? Do you have tenure?
     

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