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Kenetic Energy of a Particle due to Speed

  1. Oct 22, 2012 #1
    When a particle moves with large speed, the kinetic energy of the particle is increasing
    What really happens inside the particle?
    Can electron due to speed moves to higher electron orbits?
    If yes, how are the laws for that?
  2. jcsd
  3. Oct 22, 2012 #2


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    When talking about an object moving with a certain velocity it is important to understand that from that objects frame of reference, IT ISN'T MOVING. Think about it. If you are in a car traveling down the road, you easily say that the Earth is moving underneath you. We only make the distinction that we are moving and not the Earth because it is convenient to use the Earth as a point of reference. So nothing happens inside the particle during movement.

    Atomic and molecular orbits are far more complicated, but suffice it to say that the concept of an electron physically moving in an orbit around a nucleus is not correct. The electron is described by a wavefunction that has a range for its momentum and position and you cannot say that it is actually moving around. This is a very weird concept but an important one. Instead of speed, we have momentum and energy associated with the electron. An electron can gain energy which corrosponds to an increase in momentum, and thus be promoted to a higher "energy level", but again this shouldn't be associated with physical movement in an orbit. Any basic book or article on Quantum Mechanics should be able to explain all this in more detail.
  4. Oct 22, 2012 #3
    Related to the question is that fast moving particles in the LHC emits radiation

    Is this when these accelerate, moves with constant speed or decelerate?
    What is the cause of the radiation?
  5. Oct 22, 2012 #4
    An accelerated (charged) particle emits photons. The acceleration may be rotational so that the velocity changes direction even though the speed is unaltered. For example at a synchrotron x-rays are generated by leading a bunch of fast electrons through so-called wigglers consisting of alternating magnets. This causes the electrons to move from side to side and therefore emit x-ray photons.

    Since the LHC is a ring radiation is emitted from the particles travelling in the ring whenever they turn (their velocity change direction). I don't know if there are other effects that causes the particles to emit radiation while there are no collisions.
  6. Oct 22, 2012 #5


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    As Redsonja said, a charged particle that is accelerated will emit radiation. This takes energy from the particle and slows it down.
    This effect greatly affects our capabilities to build high energy particle accelerators because the higher the energy and the tighter the turns the more energy is lost due to Bremsstrahlung, as the effect is known. If you want to get particles up to high enough velocities you have to build massive accelerators in order to keep the turns from being too tight and putting too low of a cap on your velocity.

  7. Oct 22, 2012 #6
    Nothing happens inside a fast moving particle as stated above. Right now YOU are moving at 99.99999999% the speed of light in some observers frame.....and you are just fine!!

    Electron orbitals [allowed energy levels] are described by standing waves and different standing-waves are proportional to a possible energy level. An allowed energy level is determined by the degrees of freedom...these vary from atom to atom and also vary in different structures, like different molecules and lattices.
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