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Two Trains

Two trains are moving towards each other over two adjacent parallel tracks. The length of first train is 320 ft moving at 50 miles/h, the second one is 280 ft long moving at 40 miles/h. Find the amount of time elapsed from the moment the two trains meet until they just pass each other. 1 mile = 5280 ft.

Posted 225 day ago

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Answers (5)

JRami 		rajbaba78,
As I said in my response to another question, I would like to upload my response as a word document file, but this site is not allowing me to do it. Typing math symbols and drawing diagrams take lot of time so I know how to solve this problems but I do not want to spend that much time here.
J.Rami

Posted 223 day ago

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jayteacher 		Answer 3 should have 60s / 1 min as the last conversion.

Also, the 2 trains problem does not seem to be an Accounting and Taxes problem :-)

Posted 224 day ago

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MFB13 		Since the two trains are moving towards each other in parrellel, It would be like saying also that one of the trains is stationary and the other train is moving past the other train at

90 mi/hr = 50mi/hr - (-40mi/hr).

The second part of this problem is that you must consider how long it takes for the length of both trains to pass one another which would be 320 ft + 280 ft = 600 ft . One can also construct this model on a number line and make a diagram of two different lines passing one another being one of them stationary and the one moving at 90 mi/hr as a thought experiment (with no relativistic effects included).

Thus, we can set this problem up with the following units in mind:

(600 ft)( 1 mi/5280 ft) (1 hr/90 mi)(60 min/hr)(60 s/hr) = 4.54 s

So it takes about 4.54 seconds for both trains to pass one another completely.



Posted 224 day ago

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matherapist 		For this problem, the rate of closure is 50mph plus 40mph = 90mph. Since 60 mph = 88'/sec
[1 mi/min= 5280/60=88] then 90mph= 88+(90/60)=132'/sec. The length of the trains is
280' +320' = 600'.
So the problem reduces to how long does it take an object moving at 132'/sec to travel 600 feet.
Since Distance = rate x time (D=RT) we have 600=132 x T or T = 600/132=4.5454..........sec

Posted 224 day ago

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50miles/h = 440/6 ft/sec
40miles/h = 352/6 ft/sec

When the two trains meet, the total length of two trains will be 320 + 280 = 600 ft.
This length will shrink at a rate of 440/6 ft/sec +
352/6 ft/sec = 792/6 ft/sec
So the time elapsed when the two trains are separated = 600 ft/(792/6) ft/sec ~ 4.54 sec.
Rajden Babayan, Ph.D.
Professor of Mathematics at California State University, CSUN. (retired)

Posted 225 day ago

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