What is the ideal timetable duration for a complete train journey?

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The discussion focuses on calculating the ideal timetable duration for a complete train journey using a velocity-time graph approach. For the journey from Aytown to City, the total time calculated is 18 minutes, while the journey from Aytown to Beeburg and then to City results in a total time of approximately 21 minutes. Participants clarify the importance of correctly accounting for acceleration and deceleration distances, denoted as s1, and the need to convert minutes into seconds for accurate calculations. A mistake in the initial calculation regarding a 1-second stop was identified, leading to a revised total of 21 minutes for the complete journey. The final consensus emphasizes the need for precise calculations in timetable planning.
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Homework Statement
see attached
Relevant Equations
understanding of the ##v-t## graph
The question is below;
1639697693005.png
My approach;
and kindly note that i am comfortable in using the si units. Here i used,
##60##km/hr = ##16.66666##m/s.

For part (a),

using the ##v-t## graph,
##→s_1##=(##\frac {1}{2}##×##180×16.666)##+(##\frac {1}{2}##×##60##×##16.666##)
##=1500+500=2000##m
Total distance from Aytown to City is ##9000+7000=16000##metres
Therefore the remainder portion is ##16000-2000=14000##m. The time taken to cover this ##14000## m is given by;
##t##=##\frac{14000}{16.6666}##= ##840## seconds.
The timetable therefore should give an allowance of ##t=180+60+840=1080## seconds = ##18##
minutes.

For part (b),
using the ##v-t## graph,
Total distance from Aytown to Beeburg is ##9000##metres
##→s_1##=(##\frac {1}{2}##×##180×16.666)##+(##\frac {1}{2}##×##60##×##16.666##)
##=1500+500=2000##m
Therefore the remainder portion is ##9000-2000=7000##m. The time taken to cover this ##7000## m is given by;
##t##=##\frac{7000}{16.6666}##= ##420## seconds.

Total distance from Beeburg to City is ##7000##metres
##→s_1##=(##\frac {1}{2}##×##180×16.666)##+(##\frac {1}{2}##×##60##×##16.666##)
##=1500+500=2000##m
Therefore the remainder portion is ##7000-2000=5000##m. The time taken to cover this ##5000## m is given by;
##t##=##\frac{5000}{16.6666}##= ##300## seconds.
The timetable therefore should give an allowance of ##t=180+60+420+1+180+300+60=1201## seconds = ##20.016666##
minutes.
The time allocated should be ##21## minutes...bingo:cool:

any other approach guys...
 
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Hi @chwala ,

What is $$
s_1=(12×180×16.666)+(12×60×16.666)
$$in symbols ? And in words ?

[edit] check your units on$$
t=180+60+420+1+180+300+60=1201$$##\ ##
 
Last edited:
BvU said:
Hi @chwala ,

What is $$
s_1=(12×180×16.666)+(12×60×16.666)
$$in symbols ? And in words ?

[edit] check your units on$$
t=180+60+420+1+180+300+60=1201$$##\ ##
The units are just fine ...##1201## seconds, ##s_1## was the first portion of the ##v-t## graph...
 
##s_1## is something else !

What is the 1 second for ?

##\ ##
 
1639752348616.png


I hope this is clear for part (a)...
 
BvU said:
##s_1## is something else !

What is the 1 second for ?

##\ ##
This is for part (b) of the question, i guess i need to change the font color to distinguish between the two parts. Consider the original question they had indicated, ...at an intermediate station ##1## minute is allowed...
 
So ##s_1## is the distance needed to come up to speed and to decelerate to a stop. And to calculate it you use your favourite ##s = \frac 1 2 (v_{\rm start} + v_{\rm end})\,t\ ## which is fine.

1 second is not the same as one minute ! You want to add 60, not 1 for the stop.

Other than that, just fine. Bravo!

##\ ##
 
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BvU said:
So ##s_1## is the distance needed to come up to speed and to decelerate to a stop. And to calculate it you use your favourite ##s = \frac 1 2 (v_{\rm start} + v_{\rm end})\,t\ ## which is fine.

1 second is not the same as one minute ! You want to add 60, not 1 for the stop.

Other than that, just fine. Bravo!

##\ ##
That's right...yeah i should have converted the ##1## minute into seconds...let me post the correct solution after this post.
 
...for part (b)...

The timetable therefore should give an allowance of ##t=180+60+420+60+180+300+60=1260## seconds = ##21## minutes.
The time allocated should be ##21## minutes...bingo:cool:
 
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