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NiallBucks

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- Thread starter NiallBucks
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NiallBucks

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PWiz

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NiallBucks

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A rocket passes the earth at v=0.6c and both the rocket and earth agree it's 12:00. At t'=13:00 the rocket passes a space station. Show that the rocket passes the space station at 13:15 in the earth's frame.

Here γ=5/4

Which would I use here? Is it correct to say T=γTo so then if you sub To as 1 you'll get 1.25 which is an hour and a quarter (ie 13:15) or am I misunderstanding something?

- #6

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Why not do both? Two different solutions to a problem that agree are better than one!

- #7

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A rocket passes the earth at v=0.6c and both the rocket and earth agree it's 12:00. At t'=13:00 the rocket passes a space station. Show that the rocket passes the space station at 13:15 in the earth's frame.

Here γ=5/4

Which would I use here? Is it correct to say T=γTo so then if you sub To as 1 you'll get 1.25 which is an hour and a quarter (ie 13:15) or am I misunderstanding something?

The perfect example! Do it both ways and check you get the same answer.

- #8

MachPrincipe

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- #9

PWiz

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No, not at all. The Lorentz transformation is more fundamental in SR than time dilation and length contraction. You will only run into conceptual issues if you think otherwise.If you do so, you will gain a much deeper understanding of relativity.

It might seem easy to work your way through some problems without using the full Lorentz transformation, but you'll most definitely run into hot water if you try solving anything different from those "standard" relativity questions using the TD and LC formulae only.With practice either method will be as easy as the other.

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I completely disagree with this. Time dilation and length contraction alone cannot be used to solve problems involving the relativity of simultaneity. If your physics 101 course did not include exercises on the relativity of simultaneity then it was not enough of a curriculum to even be considered an introduction to relativity.

That is an indication of a deficiency in the course, not an indication of the sufficiency of length contraction and time dilation.

- #11

MachPrincipe

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The course was relativdly good :) It was me who didn't want to use the Lorentz transf. after understanding them. The problems included the barn and pole apparent paradox, and I solved with time dilation and length contraction alone. As said, you only need to take into account the travel time of light rays, which is the faster way of communicating events, and what lies beneath the reason of the relativity of simultaneity (Einstein original paper).I completely disagree with this. Time dilation and length contraction alone cannot be used to solve problems involving the relativity of simultaneity. If your physics 101 course did not include exercises on the relativity of simultaneity then it was not enough of a curriculum to even be considered an introduction to relativity.

That is an indication of a deficiency in the course, not an indication of the sufficiency of length contraction and time dilation.

I have studied GR at the faculty, and no need of using Lorentz transform. never in my life. Why the academical books insist on this historical and rather artificial approach is beyond my understanding.

- #12

PWiz

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I doubt it.I have studied GR at the faculty, and no need of using Lorentz transform

- #13

MachPrincipe

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You can take my word. As for special relativity, think of a problem and send me a message or post it here. I will use time dilation and lenght contraction formulaae alone. It is funny. Even with cuadrivector p_i , E... I solved by this method though they wefe a little harder.I doubt it.

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Does your knowledge of SR extend to 4-vectors and energy/momentum transformations?You can take my word. As for special relativity, think of a problem and send me a message or post it here. I will use time dilation and lenght contraction formulaae alone. It is funny. Even with cuadrivector p_i , E... I solved by this method though they wefe a little harder.

- #15

MachPrincipe

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Does your knowledge of SR extend to 4-vectors and energy/momentum transformations?

Does your knowledge of SR extend to 4-vectors and energy/momentum transformations?

Physcis 101,-introduction to. SR.

Quantum physics - SR with attention to particle physics, matter-antimatter aniquilation, Compton effect, Thomas precession.

General Relativity as a semester included in Astrophysics subject.

Analytical Mechanics and Relativity.

And yes, I solved (E,pc) problems by using time dilation and length contraction relationships. Very funny and very useful to understand relativity.

- #16

MachPrincipe

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Does your knowledge of SR extend to 4-vectors and energy/momentum transformations?

Physcis 101,-introduction to. SR.

Quantum physics - SR with attention to particle physics, matter-antimatter annihilation, Compton effect, Thomas precession.

General Relativity as a semester included in Astrophysics subject.

Analytical Mechanics and Relativity.

And yes, I solved (E,pc) problems by using time dilation and length contraction relationships. Very funny and very useful to understand relativity.

- #17

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The problems included the barn and pole apparent paradox, and I solved with time dilation and length contraction alone. As said, you only need to take into account the travel time of light rays, which is the faster way of communicating events, and what lies beneath the reason of the relativity of simultaneity (Einstein original paper).

This just sounds wrong.

- #18

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That would be energy dilation and momentum contraction then!Physcis 101,-introduction to. SR.

Quantum physics - SR with attention to particle physics, matter-antimatter aniquilation, Compton effect, Thomas precession.

General Relativity as a semester included in Astrophysics subject.

Analytical Mechanics and Relativity.

And yes, I solved (E,pc) problems by using time dilation and length contraction relationships. Very funny and very useful to understand relativity.

- #19

MachPrincipe

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Haha... Nobel prize for me, then. :)That would be energy dilation and momentum contraction then!

You can make p = mv. E = mc^2. m=m_0 * gamma.

Now you just get the v' for a particle and you are done. For v' you could use velocity transfor. formulae, but I didn't myself to use Lorentz, can be done

.with v=x/t alone for constant speed. Just think a little: it is just «low level Relativity».

s

- #20

PWiz

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I'm curious as to how you can use that formula without acknowledging the fact that you're utilizing the Lorentz transformation.you could use velocity transfor. formulae,

- #21

MachPrincipe

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Keep reading til the end of my sentence: just because I din't allow myself to use Lorentz, I did use v=e/t or the differential relationship.I'm curious as to how you can use that formula without acknowledging the fact that you're utilizing the Lorentz transformation.

Just choose any SR problem, send it to me, and allow for aboutp 24 hours so I s

- #22

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More importantly for the purposes of this forum,Just choose any SR problem,

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- #23

MachPrincipe

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http://scitation.aip.org/content/aapt/journal/ajp/51/12/10.1119/1.13322More importantly for the purposes of this forum,please provide a professional referencethat supports/explains your claim because the way you are explaining it does not make any sense.

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