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Two trains are approaching one another from opposite directions on parallel tracks. each train is 150 ft long, but one of the trains is moving at 50 ft/sec, while the other is traveling at only 30 ft/sec. how many seconds elapse from the time the trains first begin to overlap to the time they have completely passed one another?

 Mar 20, 2020
 #1
avatar+2277 
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Lets say thatV1= velocity of first train=50 ft/s

V2= Velocity of second train=30 ft/s

 

Then, the velocity of two trains moving in opposite directions is:

Vr= V1 + V2

 

From here we know that Vr= 50+30= 80 ft/s

Therefore, the distance is going to be 150ft

So the time taken= distance/ relative velocity

t=150/80

t=1.875 s

 

Hope this helped!

 Mar 20, 2020
 #2
avatar+25986 
+1

their combined speed is  80 ft /sec

Let's stop one train and say the other is travelling the 80/ft/sec

 

When their noses touch.....the moving train moves another 15o ft.....then the trains are exactly BESIDE each other

   the moving train needs to move ANOTHER 150 ft to completely pass the other....a total of 300 ft at 80 ft/sec

 

    300 ft  /   (80 ft/sec)  = 3.75 seconds to completely pass

 Mar 20, 2020

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