Derive lorentz transform for energy

AI Thread Summary
The discussion focuses on deriving the relation E' = γ(E + βpc) using Lorentz transformations. It begins with the energy-mass equivalence E = mc² in a stationary frame and transitions to a moving frame, applying the Lorentz transform for momentum. A key point is the distinction between primed and unprimed momentum, which is crucial for the derivation. The solution involves recognizing that E' can be expressed as γm₀c², and simplifying using the Lorentz transformation for velocities. The final result is achieved by expanding γ and substituting the relevant terms.
gboff21
Messages
48
Reaction score
0

Homework Statement


Derive the relation:
E' = \gamma (E + \beta p c)

Homework Equations


p&#039; = \gamma p \\<br /> E^{2} = p^{2} c^{2} + M^{2}c^{4}

The Attempt at a Solution


start off with stationary frame S E=mc^{2}
then in moving frame S' E&#039;^{2} = p&#039;^{2} c^{2} + E^{2}:
lorent transform momentum:
E&#039;^{2} = \gamma^{2} m^{2} v^{2}c^{2} + E^{2}
and that's as far as I get!
 
Last edited by a moderator:
Physics news on Phys.org
##E=\gamma mc^2##

That "p", in the equation you are supposed to prove, is unprimed.
Is that significant?
 
Yes the p is supposed to be unprimed.

I've solved it now. Thanks anyway.
Here it is for anyone who's having the same problem:
You start off (or derive it as I had to, to understand it) with the lorentz transform for velocities in two frames u = \frac{u&#039;+v}{1+frac{uv}{c^{2}}}
Know that E&#039;=\gamma m_{0}c^{2} because in the stationary frame S, only rest mass provides energy.
You expand out gamma with u' given above and recognise that p&#039;=\gamma p
simplify and you get an answer!
 
TL;DR Summary: I came across this question from a Sri Lankan A-level textbook. Question - An ice cube with a length of 10 cm is immersed in water at 0 °C. An observer observes the ice cube from the water, and it seems to be 7.75 cm long. If the refractive index of water is 4/3, find the height of the ice cube immersed in the water. I could not understand how the apparent height of the ice cube in the water depends on the height of the ice cube immersed in the water. Does anyone have an...
Kindly see the attached pdf. My attempt to solve it, is in it. I'm wondering if my solution is right. My idea is this: At any point of time, the ball may be assumed to be at an incline which is at an angle of θ(kindly see both the pics in the pdf file). The value of θ will continuously change and so will the value of friction. I'm not able to figure out, why my solution is wrong, if it is wrong .
Back
Top