The bridge and the train have the same length at rest.[...]
The bridge collapses only if the entire weight of the train rests on
it.
[Moderator's note: This is essentially the same puzzle as the ladder
paradox, which even has its own Wikipedia entry. In fact, it is closer
to the "man falling into grate" version originally discussed by the
late, great Wolfgang Rindler. -P.H.]
The bridge and the train have the same length at rest.[...]
The bridge collapses only if the entire weight of the train rests on
it.
[Moderator's note: This is essentially the same puzzle as the ladder
paradox, which even has its own Wikipedia entry. In fact, it is closer
to the "man falling into grate" version originally discussed by the
late, great Wolfgang Rindler. -P.H.]
The version we got in class (way back when) was the train entering the
barn with the doors opening/closing just in time. The answer, of
course, is relativity of simultaneity.
On 2020-11-13, Luigi Fortunati <fortunati.luigi@gmail.com> wrote:
The bridge and the train have the same length at rest.[...]
The bridge collapses only if the entire weight of the train rests
on it.
[Moderator's note: This is essentially the same puzzle as the
ladder paradox, which even has its own Wikipedia entry. In fact,
it is closer to the "man falling into grate" version originally
discussed by the late, great Wolfgang Rindler. -P.H.]
The version we got in class (way back when) was the train entering
the barn with the doors opening/closing just in time. The answer,
of course, is relativity of simultaneity.
Bruce Scott sabato 12/12/2020 alle ore 19:13:37 ha scritto:
The bridge and the train have the same length at rest.[...]
The bridge collapses only if the entire weight of the train rests on
it.
[Moderator's note: This is essentially the same puzzle as the ladder
paradox, which even has its own Wikipedia entry. In fact, it is closer
to the "man falling into grate" version originally discussed by the
late, great Wolfgang Rindler. -P.H.]
The version we got in class (way back when) was the train entering theBut does the bridge collapse or does it not collapse?
barn with the doors opening/closing just in time. The answer, of
course, is relativity of simultaneity.
[Moderator's note: Answer per moderator's note here, as this has been
solved long ago. The bridge collapses. Forget the complication of the
bridge and the weight of the train causing it to break; just have a gap
where the bridge should be. Does the train fall into the gap? Yes.
See the "paradox" due to Rindler above. Check this out: https://www.youtube.com/watch?v=Xrqj88zQZJg I think that some of the confusion comes from first assuming that when the train is on the bridge
or the gap then it will fall, but in practice if the train were moving
that fast then it would just sail over the gap. But if you assume that
it would fall when positioned over the gap, you also have to assume that gravity is strong enough to pull it down. -P.H.]
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