How Much Kinetic Energy to Accelerate a Proton to 0.9999c?

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Homework Help Overview

The discussion revolves around calculating the kinetic energy required to accelerate a proton from rest to a velocity of 0.9999c, where c represents the speed of light. The original poster presents an equation for kinetic energy and expresses uncertainty about their calculations and results.

Discussion Character

  • Exploratory, Assumption checking, Mathematical reasoning

Approaches and Questions Raised

  • The original poster attempts to use the relativistic kinetic energy formula but questions their arithmetic and the validity of their answer. Some participants suggest there may be missing elements in the calculations. Others reference online findings that lead to different numerical results, prompting further inquiry into the derivation of certain values.

Discussion Status

Participants are actively engaging with the problem, with some offering guidance on the steps to take in calculating the kinetic energy. There is a recognition of differing interpretations and results, but no consensus has been reached on the correct approach or final answer.

Contextual Notes

Participants are grappling with the implications of relativistic effects and the proper application of the Lorentz factor in their calculations. There is also mention of confusion regarding specific numerical values encountered in online resources.

StillLearningToronto
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Thread moved from Technical Forum.
Question:

Calculate the kinetic energy required to accelerate a single proton from rest position to 0.9999c. The mass of the proton is 1.67*10^-27 kg.

Equations Used:
Ek=(mc^2/√ 1-(v^2/c^2))-mc^2

Attempt at the problem:

Ek=(1.67*10^-27kg)(3*10^8m/s)^2/√ 1-(0.9999c^2/c^2))-1.67*10^-27kg)(3*10^8m/s)^2
Ek=(1.5*10^-10/0.01)-1.5*10^-10
Ek= 1.48*10^-8

(sorry if its jumbled, I am used to writing it out in my equation editor)

I'm not fairly confident on this answer because I have found different answers online saying it was correct.

Just looking for someone to verify this, or at least point me in the right direction,
Cheers xx
 
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I didn't check your arithmetic, but an answer like "Ek= 1.48*10^-8" can never be right. Are you sure you aren't forgetting something? :oldtongue:
 
JoePhysics said:
I didn't check your arithmetic, but an answer like "Ek= 1.48*10^-8" can never be right. Are you sure you aren't forgetting something? :oldtongue:
Im very positive I am missing something.

This is what i found online:

Ekrest = mc2
Ekrest = (1.67*10^-27)(c)2
Ekrest = 1.5*10^-10

Ek= (1.5*10^-10)/√(1.9999*10^-4)-(1.5*10^-10)
EK=1.047*10^-8J

But i have NO idea how they got (1.9999*10^-4)
 
StillLearningToronto said:
But i have NO idea how they got (1.9999*10^-4)

Are you sure that everything is properly "squared" away?
 
Last edited:
StillLearningToronto said:
But i have NO idea how they got (1.9999*10^-4)
I too have no idea how they got this number or what it means, but their numerical answer 1.047×10-8 J agrees with what I got. So let me guide you through the steps that I took.
1. Write an expression for the total energy of the proton using the Lorentz factor γ.
2. Subtract the rest mass energy to find the kinetic energy of the proton.
3. Put in the numbers.
 

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