How Is the Momentum of an Electron Calculated at 0.8c?

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Homework Help Overview

The discussion revolves around calculating the momentum of an electron traveling at 0.8 times the speed of light (0.8c). Participants are exploring the implications of relativistic effects on momentum, as the classical formula may not be applicable at such high speeds.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Some participants reference the classical momentum formula (p = mv) and question its validity at relativistic speeds. Others suggest the need for a relativistic definition of momentum and mention the appropriate formula involving the rest mass of the electron.

Discussion Status

Participants are actively engaging with the problem, questioning the assumptions behind using classical mechanics at relativistic speeds. There is a mix of attempts to clarify the correct approach and explore the relativistic context, but no consensus has been reached.

Contextual Notes

Some participants note that the classical approximation is only accurate for low speeds, indicating a recognition of the limitations of the classical approach in this scenario.

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Homework Statement


What is the magnitude of the momentum (in kgm/s) of an electron traveling at 0.8c

Homework Equations


p = mv

The Attempt at a Solution


see photo. I said A but the answers said B.
 

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pkc111 said:

Homework Statement


What is the magnitude of the momentum (in kgm/s) of an electron traveling at 0.8c

Homework Equations


p = mv
p=mv is the classical approximatation accurate only for low speeds.

80% light speed is certainly not a low speed!

What is the relativistic definition of momentum?
 
Thank you!
 
pkc111 said:
What is the magnitude of the momentum (in kgm/s) of an electron traveling at 0.8c
it should be m0v/√(1-v2/c2),
m0 being the rest mass of the electron.
​
 
Last edited:

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