I respond here to a recent comment1 by Di Matteo regarding my paper “‘Relativistic’ particle dynamics without relativity.”2 In that paper, I begin by recounting a 1906 thought experiment by which Einstein3 demonstrated, completely independently of the relativity postulates, that the transport of energy E must be accompanied by an increment of mass δm = E/c2. With that result, by means of the same thought experiment using a material particle instead of a pulse of light, I demonstrate that the momentum of a particle with mass m (measured at rest), velocity v, and kinetic energy K must be given by p = (m + K/c2) v. From there, it is easy to derive the usual high-speed (“relativistic”) expressions p = mγv and K = m(γ − 1)c2, with γ being the familiar Lorentz factor (1 − v2/c2)...
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NOTES AND DISCUSSIONS|
May 01 2019
Reply to ‘Comment on “ ‘Relativistic’ particle dynamics without relativity” ’ [Am. J. Phys. 87, 144–145 (2019)] Available to Purchase
Allan Walstad
Allan Walstad
a)
Physics Department, University of Pittsburgh at Johnstown
, Johnstown, Pennsylvania 15904
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Allan Walstad
a)
Physics Department, University of Pittsburgh at Johnstown
, Johnstown, Pennsylvania 15904a)
Electronic mail: [email protected]
Am. J. Phys. 87, 401 (2019)
Article history
Received:
February 26 2019
Accepted:
March 12 2019
Connected Content
This is a commentary to:
Comment on “Relativistic particle dynamics without relativity” [Am. J. Phys. 86, 747–749 (2018)]
Citation
Allan Walstad; Reply to ‘Comment on “ ‘Relativistic’ particle dynamics without relativity” ’ [Am. J. Phys. 87, 144–145 (2019)]. Am. J. Phys. 1 May 2019; 87 (5): 401. https://doi.org/10.1119/1.5095944
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