simultaneity (1 Viewer)

[Premus]

Hey

I know this question has been asked before...but i just want to confirm it.

A train is moving to the right , close to the speed of light. There are two observers , one outside the train and one in the middle of the train
CASE A - two lights on either side INSIDE the train are turned on.
CASE B - two lightning strikes on either side of the train ( Outside, obviously! )

What does each observer notice about the light in CASE A and CASE B?

are there any other ways they can ask us to analyse simultaneity questions?
Also, with time dilation, length contraction, mass dilation....are there any tricky ways they can ask questions ??

Thanks a bunch

 

[neuro_logik]

There was a question on the 2004 CSSA Physics Trial dealing with Simltaneity, where there was a person standing on a train platform and there was a train passing, where there were 2 lighting strikes on the front and back of the train. You had to identify which would lighting strikes would the observers see first, etc and explain it.

 

[acmilan]

I think most likely if they ask about simultaneity it would be to describe a thought experiment that demonstrates it OR they might ask what consequences resulted from special relativity, in this case you can list the things you mentioned

 

[helper]

When in doubt look at the syllabus
explain qualitatively and quantitatively the consequence of special relativity in relation to:
– the relativity of simultaneity

So if they ask they will look at a situation like described above and have you explain it. They may want you to describe what is meant by relativity of simuality or extend it to describe the effect of it on time and length

 

[Premus]

i think u guys misinterpreted my post..

i was asking what each observer would notice about the light beams and lightning strikes in CASE A and CASE B , cause im uncertain!

Thanks

 

[acmilan]

Hey

are there any other ways they can ask us to analyse simultaneity questions?
Also, with time dilation, length contraction, mass dilation....are there any tricky ways they can ask questions ??

Thanks a bunch

You also asked the question above and thats what everyone is answering

Hey

I know this question has been asked before...but i just want to confirm it.

A train is moving to the right , close to the speed of light. There are two observers , one outside the train and one in the middle of the train
CASE A - two lights on either side INSIDE the train are turned on.
CASE B - two lightning strikes on either side of the train ( Outside, obviously! )

What does each observer notice about the light in CASE A and CASE B?

As for this question, the answer assumes that the two observers are exactly in line with each other and the light and lightning are equidistant from both sides of the two observers.

CASE A - the guy in the train sees the lights simultaneous, the guy outside sees the light on the left turn on first

CASE B - the guy outside sees the lightning strikes as simultaneous, the guy inside sees the lightning on the right first

Hence events simultaneous in one inertial frame of reference are not simultaneous in another fram of reference

 

[Premus]

" CASE A - the guy in the train sees the lights simultaneous, the guy outside sees the light on the left turn on first "

i understand that the guy in the train sees the light sumultaneously, but could you pls explain why the the guy outside sees the light on the left turn on first ?

Thank you

 

[tennille]

You said the train was travelling to the right. Maybe because the right side is receding from the person outside and the left side is approaching the person causes him/her to see the left side flash first.

 

[tennille]

That is just a guess, though. You might want to check that.

 

[Xayma]

Actually if the lights were inside the carriage you would see them at the same time. With a blue or red shift.

You would however see the light strike the left side of the carriage before the right side, while the person inside would see it strike both sides at once.

 

[zeropoint]

Hey

I know this question has been asked before...but i just want to confirm it.

A train is moving to the right , close to the speed of light. There are two observers , one outside the train and one in the middle of the train
CASE A - two lights on either side INSIDE the train are turned on.
CASE B - two lightning strikes on either side of the train ( Outside, obviously! )

What does each observer notice about the light in CASE A and CASE B?

are there any other ways they can ask us to analyse simultaneity questions?
Also, with time dilation, length contraction, mass dilation....are there any tricky ways they can ask questions ??

Thanks a bunch

Okay, I'm gonna make this short and sweet as I have an english HSC exam the day after tomorrow. If the outside observer O is equidistant from either end of the train at the instant the flashes of lightning strike opposite ends of the train, he will argue that the flashes originate from the hypothetical stationary ``char marks'' on the ground, since the speed of light is constant and he is equidistant from either event, then the fact that he ``sees'' the flashes at the same time allows him to conclude that the events are simultaneous . To the inside observer O', the origins of the lightning flashes are also stationary in her frame of reference due to the isotropy of light. In her frame of reference the flashes originate from the equidistant ends of the train and travel ``different'' distances to arrive at the the outside observer O at the _same time_. Since the speed of light is constant, the light rays must have departed at different times to arrive at O simultaneously. Hence the relativity of simultaneity.