How fast will the electron be travelling?

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Homework Help Overview

The discussion revolves around calculating the speed of an electron using classical kinetic energy formulas. Participants are examining the implications of their calculations, particularly in the context of relativistic effects when high speeds are involved.

Discussion Character

  • Exploratory, Assumption checking, Conceptual clarification

Approaches and Questions Raised

  • Participants are attempting to derive the speed of an electron from its kinetic energy using the formula Ek = ½ MV^2. Questions arise regarding the validity of using classical mechanics for high-speed particles and the implications of their calculations suggesting speeds exceeding the speed of light.

Discussion Status

Some participants have pointed out the need to consider relativistic effects when dealing with high velocities. There is acknowledgment of potential errors in classical assumptions, and one participant suggests verifying with an instructor, indicating a productive direction in the discussion.

Contextual Notes

Participants are discussing the limitations of classical physics in the context of high-energy electrons, particularly the assumption that classical formulas can apply without adjustments for relativistic speeds.

Brooke22
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How fast will the electron be travelling?

Ek = ½ MV^2
V = 2Ek/M
V = √2Ek/M
= √ 2 x 1.6x10^-19/9.1 x 10^-31
= ?
This number is too high since it implies that a larger voltage (say 10) would make the electron travel faster than light. The reason is?
 
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You might want to give at least SOME info about the problem and what you're trying to do.
Were you solving E=1/2mv^2 for v?

By the way. You're using the classical formula 1/2mv^2 for the kinetic energy. Ofcourse you can get velocities faster than light if you don't take relativity into account.
 
That's right. When doing with high speed, you have to apply the relative theory.[/color]
 
Brooke22 said:
How fast will the electron be travelling?

Ek = ½ MV^2
V = 2Ek/M
V = √2Ek/M
= √ 2 x 1.6x10^-19/9.1 x 10^-31
= ?
This number is too high since it implies that a larger voltage (say 10) would make the electron travel faster than light. The reason is?

That doesn't mean your answer might not be correct. I've found that kind of mistake in any number of Introductory level texts. Check with your instructor.

-Dan
 

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