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 2021-04-11, 08:34 #1 retina Undefined     "The unspeakable one" Jun 2006 My evil lair 6,143 Posts Doubling your average speed? You are at the beginning of a perfectly flat and perfectly straight section of road that is exactly 1000 metres long (d = 1000 metres). You are wearing a Super-Chronograph 9000 stopwatch which can measure time precisely without any error. At the beginning of the road section you start the timer on your Super-Chronograph 9000 and travel to the other end of the road. When you reach the far end you note the elapsed time (t1 = 1000 seconds) and compute the average speed (v1 = d / t1). You then instantly turn around and start to travel back to the beginning. When you reach the beginning again you stop the timer (t2) and compute your overall average speed as (v2 = 2 * d / t2). At what speed must you travel during the return to have (v2 = 2 * v1)? I spell metre with '...re', too bad, just accept it, hah!
 2021-04-11, 10:09 #2 slandrum   Jan 2021 California 10001012 Posts You have to travel back instantaneously.
2021-04-11, 10:18   #3
retina
Undefined

"The unspeakable one"
Jun 2006
My evil lair

6,143 Posts

Quote:
 Originally Posted by slandrum You have to travel back instantaneously.
Please give the answer to the question.
Quote:
 Originally Posted by retina At what speed must you travel during the return to have (v2 = 2 * v1)?

 2021-04-11, 10:33 #4 slandrum   Jan 2021 California 1058 Posts Well, since you are measuring the time by your own watch that you are taking with you, you have to travel back in 0 time, so you have to travel at c (the speed of light). If you were not in a relativistic space and there was an absolute time reference, there's no speed at which you could travel back to double your average speed. Last fiddled with by slandrum on 2021-04-11 at 10:34
2021-04-11, 11:07   #5
retina
Undefined

"The unspeakable one"
Jun 2006
My evil lair

6,143 Posts

Quote:
 Originally Posted by slandrum Well, since you are measuring the time by your own watch that you are taking with you, you have to travel back in 0 time, so you have to travel at c (the speed of light).
That is the correct answer.

People here are too smart to fool so easily.
Quote:
 Originally Posted by slandrum If you were not in a relativistic space and there was an absolute time reference, there's no speed at which you could travel back to double your average speed.
What about travelling at infinite speed?

2021-04-11, 13:00   #6
xilman
Bamboozled!

"πΊππ·π·π­"
May 2003
Down not across

2·72·109 Posts

Quote:
 Originally Posted by slandrum Well, since you are measuring the time by your own watch that you are taking with you, you have to travel back in 0 time, so you have to travel at c (the speed of light). If you were not in a relativistic space and there was an absolute time reference, there's no speed at which you could travel back to double your average speed.
Quantum tunnelling?

https://en.wikipedia.org/wiki/Quantu...ter_than_light

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