STANDARD PHYSICS EDUCATION (introduces ABSURDITY):
"Two bombs lie on a train platform, a distance L
apart. As a train passes by at speed v, the bombs
explode simultaneously (in the platform frame) and
leave marks on the train. Due to the length
contraction of the train, we know that the marks on
the train will be a distance gamma.L apart when viewed
in the train's frame (since this distance is what is
length-contracted down to the given distance L in the
platform frame). How would someone on the train
quantitatively explain to you why the marks are
gamma.L apart, considering the bombs are only a
distance L/gamma apart in the train frame?"
http://www.courses.fas.harvard.edu/~phys16/Textbook/ch10.pdf
p.46
HONEST PHYSICS EDUCATION (would introduce REDUCTIO AD
ABSURDUM):
Two unbreakable barriers are installed on a train
platform, a distance L apart. As a train passes by at
speed v, the barriers fall simultaneously (in the
platform frame) and block the railway. The proper
length of the train is greater than L but, due to the
length contraction of the train, right before the
barriers fall, the observer in the platform frame sees
the train occupying only a short segment of the
distance between the barriers. In other words, the
observer sees the barriers catching the train. How
long is the caught train?
Pentcho Valev
____________________________________________________________________________________
We have the perfect Group for you. Check out the handy changes to Yahoo! Groups
(http://groups.yahoo.com)
|