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

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SUMMARY

The kinetic energy required to accelerate a proton from rest to 0.9999c is calculated using the equation Ek=(mc^2/√(1-(v^2/c^2)))-mc^2. The mass of the proton is 1.67×10^-27 kg, leading to a rest energy of approximately 1.5×10^-10 J. The correct kinetic energy value is approximately 1.047×10^-8 J, derived by applying the Lorentz factor γ and subtracting the rest mass energy. The calculations confirm that the initial answer of 1.48×10^-8 J was incorrect due to misapplication of the equations.

PREREQUISITES
  • Understanding of relativistic physics concepts, particularly kinetic energy and the Lorentz factor.
  • Familiarity with the equation for relativistic kinetic energy: Ek=(mc^2/√(1-(v^2/c^2)))-mc^2.
  • Basic knowledge of proton mass, specifically 1.67×10^-27 kg.
  • Ability to perform calculations involving the speed of light, c, approximately 3×10^8 m/s.
NEXT STEPS
  • Learn about the Lorentz factor and its application in relativistic physics.
  • Study the derivation of the relativistic kinetic energy equation.
  • Explore the implications of high-speed particle physics and energy calculations.
  • Utilize computational tools like Wolfram Alpha for complex physics calculations.
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Students and professionals in physics, particularly those focused on particle physics and relativistic mechanics, will benefit from this discussion.

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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