SOLUTION: How long is the train?
A train moving 45 kilometres per hour meets and is passed by a train moving 36 kilometres per hour. A passenger in the first train sees the second train t
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Question 954712: How long is the train?
A train moving 45 kilometres per hour meets and is passed by a train moving 36 kilometres per hour. A passenger in the first train sees the second train take 6 seconds to pass him. How long is the second train?
Found 2 solutions by ankor@dixie-net.com, Theo:
Answer by ankor@dixie-net.com(22740) (Show Source): You can put this solution on YOUR website!
A train moving 45 kilometres per hour meets and is passed by a train moving 36 kilometres per hour.
A passenger in the first train sees the second train take 6 seconds to pass him.
How long is the second train?
:
The relative speed of the two trains is 45 + 36 = 81 km/h
:
At this speed how far can it go in 6 sec
:
= 22.5 meter/sec
6 * 22.5 = 135 meters is the length of the 2nd train
Answer by Theo(13342) (Show Source): You can put this solution on YOUR website!
A train moving 45 kilometres per hour meets and is passed by a train moving 36 kilometres per hour. A passenger in the first train sees the second train take 6 seconds to pass him. How long is the second train?
the trains are traveling in opposite directions, so their rates relative to each other are additive.
the net rate of travel is 45 + 36 = 81 kmph.
if the second train was standing still, it would seem like the first train was passing it at 81 kmph.
if the first train was standing still, it would seem like the second train was passing it at 81 kmph.
the passenger in the first train sees the second train for 6 seconds.
81 kmph is equivalent to 81 / 3600 = .0225 kmps (kilometers per second)
multiply that by 6 seconds and you get a distance of 6 * .0225 = .135 km.
that's because rate * time = distance and so .0225 kmps * 6 seconds = .135 km.
the train is .135 km in length.
this is because the passenger in the first train sees the front of the second train and 6 seconds later sees the back of the second train.
there are 3280.84 feet per kilometer, so the train is .135 * 3280.84 = 442.9134 feet in length.
you can also think of this another way.
the trains are traveling at 45 kmph and 36 kmph in opposite directions.
45 kmph is equivalent to 45 / 3600 = .0125 kmps (kilometers per second).
36 kmph is equivalent to 36 / 3600 = .01 kmps.
the passenger sees the front of the second train.
6 seconds the passenger sees the back of the second train.
in those 6 seconds.
the first train has traveled 6 * .01 = .06 km in one direction.
the second train has traveled 6 * .0125 = .075km in the other direction.
the distance between the front and the back of the second train has to be .06 plus .075 = .135 km.
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