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Optimization Train Problem

  • Thread starter Delber
  • Start date
  • #1
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Homework Statement


A train leaves the station at 10:00 and travels due south at a speed of 60 km/h. Another train has been heading due west at 45 km/h and reaches the same station at 11:00. At what time were the two trains closest together?

Homework Equations


[tex]c^{2}=a^{2}+b^{2}[/tex]


The Attempt at a Solution


The trouble I am having is the wording of the question. I think it means the trains left from two different stations and will arrive at the same time together at one station. So the equation for that scenario is:

[tex]f(t) = \sqrt{(60-60t)^{2}+(45t)^{2}}[/tex]

However I get a range outside the limit of one hour. I think I'm just confused about he wording if someone can clarify it for me. Any help is appreciated.
 

Answers and Replies

  • #2
tiny-tim
Science Advisor
Homework Helper
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Homework Statement


A train leaves the station at 10:00 and travels due south at a speed of 60 km/h. Another train has been heading due west at 45 km/h and reaches the same station at 11:00. At what time were the two trains closest together?
Hi Delber! :smile:

It means train 2 arrives at the same station one hour after train 1 left. :smile:
 
  • #3
19
0
Thanks for the clarification.

So the new equation should be:

[tex]f(t)=\sqrt{(45-45t)^{2}+(60t)^{2}}[/tex]?

Edit: Yep, I get the correct answer in the book. Thanks for the help.
 
Last edited:

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