Particle´s acceleration respect two inertial frames

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Homework Help Overview

The discussion revolves around the transformation of acceleration between two inertial frames, S and S', where S' moves with a constant velocity relative to S. The original poster presents a problem involving a particle with constant acceleration in the S' frame and seeks to determine its acceleration as observed from the S frame using Lorentz transformations.

Discussion Character

  • Conceptual clarification, Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • Participants explore the use of velocity transformation formulas and question the appropriateness of differentiating with respect to proper time. There is discussion about the notation used for acceleration in different frames, and some participants express confusion regarding the definitions and transformations involved.

Discussion Status

Some participants have provided guidance on starting with the velocity transformation and deriving acceleration from it. The conversation reflects a mix of attempts to clarify notation and explore the mathematical relationships without reaching a definitive conclusion.

Contextual Notes

There is mention of corrections made by a teacher regarding the notation of acceleration in the two frames, which adds to the complexity of the discussion. Participants are also navigating the implications of using proper time in their calculations.

Aler93
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Homework Statement


System S' moves with constant speed v=(vx,0,0) respect to the system S. On the S' system a particle moves with a constant acceleration a=(ax,ay,az).
What is the acceleration a'=(ax',ay',az') measured from the system S?.

Homework Equations


Lorentz transformation

The Attempt at a Solution


[/B]
I use the velocity-addition formula and find the ecuations of the velocity transformation, I think maybe a derivation respect to proper time of the velocity transformation ux',uy',uz' give the aceleration of the particle, but I am not really sure how to do it.


 
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Aler93 said:

Homework Statement


System S' moves with constant speed v=(vx,0,0) respect to the system S. On the S' system a particle moves with a constant acceleration a=(ax,ay,az).
What is the acceleration a'=(ax',ay',az') measured from the system S?.
The notation is confusing. You have the unprimed a for the acceleration as measured in the primed frame S, and you have the primed a' for the acceleration as measured in the unprimed frame S.
 
TSny said:
The notation is confusing. You have the unprimed a for the acceleration as measured in the primed frame S, and you have the primed a' for the acceleration as measured in the unprimed frame S.

I know, but I´m using the same notation that it´s used in the problem. Solving the problem I´m finding the unprimed acceleration as its seen from the system S.
 
Aler93 said:
I know, but I´m using the same notation that it´s used in the problem. Solving the problem I´m finding the unprimed acceleration as its seen from the system S.

Well, it's confusing to me. But let's see how it goes.

I agree that starting with the velocity transformation formula is a good idea. I'm not sure why you would want to differentiate with respect to proper time. The acceleration of the particle in frame S would be the derivative of the velocity of the particle in frame S with respect to time as measured in frame S. Similarly for frame S'.
 
TSny said:
Well, it's confusing to me. But let's see how it goes.

I agree that starting with the velocity transformation formula is a good idea. I'm not sure why you would want to differentiate with respect to proper time. The acceleration of the particle in frame S would be the derivative of the velocity of the particle in frame S with respect to time as measured in frame S. Similarly for frame S'.

I talk with the teacher and he made some corrections:
System S' moves with constant speed v=(vx,0,0) respect to the system S. On the S' system a particle moves with a constant acceleration a'=(ax',ay',az').
What is the acceleration a'=(ax,ay,az) measured from the system S?.

In this case I used the inverse lorentz transformation cause its from the S system and obtain something like
Code:
[ tex ]ux=\frac{u_x'+v}{1+frac{u_x' v}{c^2}}[ /tex ]
and
Code:
uy=\frac{uy'}{ \gamma(1+ ux'v/c^2)}

To find the acelleration we derive respect to dt, as you said, I was a bit confused, but it depents of proper time τ

a=du/dt=du/dτ dτ/dt

but how i use this equation with the velocitiy formulas we found before?
 
Last edited:
Aler93 said:
$$u_x=\frac{u_x'+v}{1+\frac{u_x' v}{c^2}}$$
$$u_y=\frac{u_y'}{ \gamma(1+ u_x'v/c^2)}$$To find the acelleration we derive respect to dt, as you said, I was a bit confused, but it depents of proper time τ

a=du/dt=du/dτ dτ/dt

but how i use this equation with the velocitiy formulas we found before?

When finding ##a_x = \frac{du_x}{dt}##, you can work with differentials. Thus ##a_x## equals the differential ##du_x## divided by the differential ##dt##.

For ##du_x##, use your formula above. For ##dt##, use the appropriate Lorentz transformation equation.
 
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TSny said:
When finding ##a_x = \frac{du_x}{dt}##, you can work with differentials. Thus ##a_x## equals the differential ##du_x## divided by the differential ##dt##.

For ##du_x##, use your formula above. For ##dt##, use the appropriate Lorentz transformation equation.
TSny said:
When finding ##a_x = \frac{du_x}{dt}##, you can work with differentials. Thus ##a_x## equals the differential ##du_x## divided by the differential ##dt##.

For ##du_x##, use your formula above. For ##dt##, use the appropriate Lorentz transformation equation.

Thanks, I was complicating myself, I finally obtained the three acceleration transformations.

Thanks for your help!
 

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