A relativity problem (train & platform)

[MeJennifer]

Whoa. I'm NOT saying the train ends up 10km long. I'm saying that's not factual, but is an illustration of where the looseness of the thought experiment takes us. And I'm saying that if the train stopped in the middle of the platform the front of the train DID NOT pass the front of the platform.

Don't be rude, MeJennifer.

I am not sure anymore what you are saying

Does the train pass the end of the platform: YES
Does the train get longer when it decellerates from the perspective of the frame of the platform: YES
Does the train get longer when it is stopped than the length as measured in the train's restframe: NO

Do you agree?

 

[JesseM]

Whoa. I'm NOT saying the train ends up 10km long. I'm saying that's not factual, but is an illustration of where the looseness of the thought experiment takes us. And I'm saying that if the train stopped in the middle of the platform the front of the train DID NOT pass the front of the platform.

If the train does not remain rigid, then the train can elongate, and it definitely will if each part accelerates instantaneously. And if you add something like the Born rigidity condition, the train must accelerate over an extended period, so even if the middle of the train begins to accelerate at the moment it passes the middle of the platform, it may not stop until it has passed the end of the platform.

 

[Farsight]

Yes of course I agree MeJennifer. Sorry if I wasn't very clear but please reread my posts. Thank you for that Jesse.