4-vector law of motion in different inertial frames

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SUMMARY

The discussion centers on demonstrating that Newton's second law of motion, expressed in Minkowski space as 𝖸F = m(c𝖳𝗀𝖳, 𝖳𝗀𝖳v + 𝖳𝖳𝖲a), retains its form across all inertial frames. The key to this demonstration lies in the assumption that 4-momentum is a vector, allowing the right-hand side to be expressed as the derivative of 4-momentum with respect to proper time 𝗔. Alternatively, applying the Lorentz transformation can also validate this, although it involves complex algebra that is prone to errors.

PREREQUISITES
  • Understanding of Minkowski space and its implications in physics.
  • Familiarity with 4-momentum and its properties as a vector.
  • Knowledge of the Lorentz transformation and its application in relativistic physics.
  • Basic calculus, particularly differentiation with respect to proper time.
NEXT STEPS
  • Study the derivation of 4-momentum in special relativity.
  • Learn about the implications of Lorentz transformations on physical laws.
  • Explore the mathematical foundations of Minkowski space.
  • Investigate the relationship between 3-velocity, 3-acceleration, and their relativistic counterparts.
USEFUL FOR

Physicists, students of relativity, and anyone interested in the mathematical foundations of motion in different inertial frames.

Wox
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Newton's second law of motion is given in Minkowski space by
[tex]\bar{F}=m(c\gamma\dot{\gamma}, \gamma\dot{\gamma}\tilde{v}+\gamma^{2}\tilde{a})[/tex]
where [itex]\dot{\gamma}=\frac{d\gamma}{dt}=\frac{\gamma^{3}}{c^{2}}\tilde{v}\cdot\tilde{a}[/itex] and [itex]\tilde{v}(t)[/itex] and [itex]\tilde{a}(t)[/itex] the 3-velocity and 3-acceleration. How can I show now that this law has the same form in all inertial frames?
 
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Well, it depends on what you want to assume. If you start from 4-momentum being a vector, then the RHS is d/dτ of 4-momentum (that should be easy for you to show). That is sufficient to to establish it has the same form in any inertial frame.

If, instead, you are supposed to demonstrate by brute force, it will work that applying the Lorentz transform should produce the same form, but that will be a large amount of messy, error prone algebra.
 

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