Half of Energy: Where Does It Go? (Solving e=mv^2)

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Discussion Overview

The discussion revolves around the relationship between energy and kinetic energy, specifically questioning the derivation of the equation e=mv^2 and its connection to the classical kinetic energy formula of 1/2mv^2. Participants explore the implications of these equations in both classical and relativistic contexts.

Discussion Character

  • Debate/contested
  • Technical explanation

Main Points Raised

  • One participant asserts that combining the equations for wavelength and energy leads to e=mv^2, but questions where the other half of the energy is in relation to the classical kinetic energy formula.
  • Another participant clarifies that the 1/2mv^2 expression is valid only in classical mechanics for low velocities and introduces the relativistic kinetic energy formula T = mc^2(γ-1) as a more accurate representation at high velocities.
  • A third participant suggests that the initial formulas used may be incorrect and requests clearer explanations and sources for the formulas being referenced.

Areas of Agreement / Disagreement

Participants express differing views on the validity of the formulas used and the context in which they apply. There is no consensus on the correctness of the initial claims or the interpretation of energy in this context.

Contextual Notes

Participants highlight the distinction between classical and relativistic mechanics, indicating that assumptions about velocity significantly affect the applicability of the formulas discussed.

ankitpandey
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combining wavelength(&)=h/mv and e=hv/& , we get e=mv^2
but kinetic energy is 1/2mv^2. where is other half?
 
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ankitpandey said:
combining wavelength(&)=h/mv and e=hv/& , we get e=mv^2
but kinetic energy is 1/2mv^2. where is other half?
Kinetic energy only takes the form 1/2mv2 in classical mechanics, which is only valid for low velocities. The full expression for relativistic kinetic energy is

[tex]T = mc^2\left(\gamma-1\right)[/tex]

You should also note that your first two expression are only valid for v = c.
 
You might want to start with formulas that are actually correct, and not confuse relativistic stuff with non-relativistic stuff. Can you explain more clearly what formulas you're using and where you got them from? If you need greek symbols and don't know LaTeX, copy and paste from Redbelly98's https://www.physicsforums.com/blog.php?b=347 .
 
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THANKS, Hootenanny
 

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