# how much time did the train need?

crazyblue
Posers and Puzzles 08 Jan '06 17:40
1. 08 Jan '06 17:40
a couple is on a bike tour along a railroad track. he has a problem with his bike, so he tells her "keep driving, ill catch up soon". when he fixed his bike he starts driving again. after a short time there comes a train, that needs 36 seconds to pass him completely. after another 18 seconds he can see how the beginning of the train reaches his wife, then there's a turn so she gets out of his sight.
when he reaches his wife, she tells him "i checked the time: from the moment the end of the train reached me, it took your 4 minutes to catch up with me."
now he wants to know, how much time the train needed to pass his wife? (they all had constant speed)
2. Wibble Wobble
Action barbie
08 Jan '06 18:18
Originally posted by crazyblue
a couple is on a bike tour along a railroad track. he has a problem with his bike, so he tells her "keep driving, ill catch up soon". when he fixed his bike he starts driving again. after a short time there comes a train, that needs 36 seconds to pass him completely. after another 18 seconds he can see how the beginning of the train reaches his wife, then ...[text shortened]... nts to know, how much time the train needed to pass his wife? (they all had constant speed)
I dont see how you can tell. The train or person could have changed speeds. You need to say the distances i think ðŸ˜•

Also why would you care? ðŸ˜€
3. 08 Jan '06 22:35
4. Trains44
Full speed locomotiv
09 Jan '06 16:49
Originally posted by crazyblue
a couple is on a bike tour along a railroad track. he has a problem with his bike, so he tells her "keep driving, ill catch up soon". when he fixed his bike he starts driving again. after a short time there comes a train, that needs 36 seconds to pass him completely. after another 18 seconds he can see how the beginning of the train reaches his wife, then ...[text shortened]... nts to know, how much time the train needed to pass his wife? (they all had constant speed)
Depends.......Is it train44?
5. 09 Jan '06 16:55
Originally posted by crazyblue
a couple is on a bike tour along a railroad track. he has a problem with his bike, so he tells her "keep driving, ill catch up soon". when he fixed his bike he starts driving again. after a short time there comes a train, that needs 36 seconds to pass him completely. after another 18 seconds he can see how the beginning of the train reaches his wife, then ...[text shortened]... nts to know, how much time the train needed to pass his wife? (they all had constant speed)
36s

I know it says the speed is constant but is the velocity? As I am assuming it is otherwise I couldn't tell.

Also you ride a bike you don't drive it.
6. 09 Jan '06 18:03
Originally posted by Will Everitt
36s

I know it says the speed is constant but is the velocity? As I am assuming it is otherwise I couldn't tell.

Also you ride a bike you don't drive it.
a) If the train took 36s, the man would be as fast as the woman. He would never reach her then right?

b) I guess I meant velocity (translated it from German). I could never figure out what the difference between speed and velocity is ðŸ˜‰

c) Okay I will ride my bike from now on ðŸ™‚
7. XanthosNZ
Cancerous Bus Crash
10 Jan '06 01:46
Speed is a scalar value. It doesn't have a direction component. Velocity is a vector value, it contains both a direction component and a magnitude component. In this case you can assume that speed is constant (velocity isn't as there is a bend mentioned).

After working on this for a while I can't see how it can be solved. I've got equations for the solution but they contain both 'distance between the riders at the point where the end of the train reaches the man' and 'the length of the train'. Anything I try gives negative answers which can't be right.
8. TheMaster37
Kupikupopo!
11 Jan '06 11:45
I need one more number.

Either the length of the train, the time the man needed for his fix or the distance between man and wife on the moment the train reached the man.
9. Trains44
Full speed locomotiv
11 Jan '06 16:39
Originally posted by TheMaster37
I need one more number.

Either the length of the train, the time the man needed for his fix or the distance between man and wife on the moment the train reached the man.
Was it a 2-8-8-0 steam loco? Was it an Amtrak Genisis 11 diesel? Was it an SNCF British class 91 electric or an LNWR "G" CLASS 0-8-0? That would help for the answer.
10. 12 Jan '06 02:20
29.75s
11. 12 Jan '06 09:58
Originally posted by Balla88
29.75s
How did you get that?

I thought there wasn't enough information to calculate (based on other posts) so I didn't bother.
12. 17 Jan '06 21:39
Originally posted by crazyblue
a) If the train took 36s, the man would be as fast as the woman. He would never reach her then right?

b) I guess I meant velocity (translated it from German). I could never figure out what the difference between speed and velocity is ðŸ˜‰

c) Okay I will ride my bike from now on ðŸ™‚
Well nobodys got it so can we have an answer? Also how you got to the answer.
13. PBE6
Bananarama
17 Jan '06 23:13
I got 30s using the solver function on MS Excel, but only after massaging the starting guesses to avoid negative solutions. I used 5 constants: v(man), v(woman), v(train), L(train), and dist0(woman-man) - I assumed the "short time" between the man starting up and the train arriving was 0. But regardless, there are more unknowns in this problem than pieces of information given (only 4). Therefore, as has already been stated in this thread, the problem is unsolvable.
14. 22 Jan '06 09:13
Just wanted to move this to the top. I am currious about the solution.

GV
15. XanthosNZ
Cancerous Bus Crash
22 Jan '06 21:38