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Re: SR examination question



Thanks to John for the nice S-T diagram and associated analysis, I'll quote
only one small portion of his excellent post:



Bottom line: Unless the context has established whose constant-time
contours are to be used (or unless the events in question are
colocated in
space), any question that begins
"When ...."
is an automatic loser. The rest of the question doesn't even
matter.


Well stated! And is IMO the crux of the matter.

However, the question stated:

"Peter and Jane are each wearing a wristwatch with a second hand that takes
one minute to make one complete revolution and Peter is moving at a speed
of 0.9c with respect to Jane. When Peter observes the second hand on his
watch to have made one complete revolution, how many revolutions will Jane
observe the second hand of her watch to have made?"

The last part "how many revolutions will *Jane
observe* the second hand of her watch to have made?" could be inferred as
"unambigously" establishing the context that its Jane's constant-time lines
(lines of simultaneity) that are to be used in answering the question.
Which gives the 2.3 second answer.

If the author had intended somebody elses constant time lines, I imagine
they would have stated "how many revolutions will Peter observe Jane's clock
. . . " or "how many revolutions does John Denker observe Jane's clock . . .
"

Denker would of course, would use the Denker frame of reference constant
time lines, the horizontal green lines, (or ones parallel to it.)