SOLUTION: A train moves with a constant velocity v = 20 m/s while passing through a 200-m long tunnel. If 15 s elapse between the moment the front of the train enters the tunnel, and when th

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Question 834802: A train moves with a constant velocity v = 20 m/s while passing through a 200-m long tunnel. If 15 s elapse between the moment the front of the train enters the tunnel, and when the back of the train leaves
the tunnel, how long is the train?
I'm not to sure on this one, I figured maybe take 200m/15s but that doesn't take the velocity into account.

Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
A train moves with a constant velocity v = 20 m/s while passing through a 200-m long tunnel.
If 15 s elapse between the moment the front of the train enters the tunnel, and when the back of the train leaves
:
Using the front of the train as ref. It travels 200m, to the end of the tunnel
then has to travel the length (t) of the train, for the train to clear the tunnel
the total dist traveled then = (t+200)
:
dist/speed = time
%28%28t%2B200%29%29%2F20 = 15
t + 200 = 20(15)
t + 200 = 300
t = 300 - 200
t = 100 meters is the length of the train
:
:
That's a pretty fast train
%2820%2A3600%29%2F1000 = 72 km/h