SOLUTION: A train T1 moving at an average speed of 90 km/h takes 8 seconds to completely cross a bridge that is 80 meters long. Another train T2 which is 155 meters long and moving in the op

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Question 1195335: A train T1 moving at an average speed of 90 km/h takes 8 seconds to completely cross a bridge that is 80 meters long. Another train T2 which is 155 meters long and moving in the opposite direction on a parallel track at an average speed of 108 km/h is just beginning to pass trainT1. Calculate the time in seconds that it takes for the two trains to completely pass one another.
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
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A train T1 moving at an average speed of 90 km/h takes 8 seconds to completely cross a bridge that is 80 meters long.
Another train T2 which is 155 meters long and moving in the opposite direction on a parallel track at an average speed of 108 km/h is just beginning to pass trainT1.
Calculate the time in seconds that it takes for the two trains to completely pass one another.
:
Train 1: Find the distance, in meters, it travels in 1 sec at 90 km/h
m/sec = %2890000%2F3600%29
m/s = 25 m/sec
then
8 * 25 = 200 meters in 8 sec
The bridge is 80 meters so the train is 200-80 = 120 meters long
:
Train 2:
Find the dist in meters the train travels in 1 sec at 108 km/h
m/s = 108000%2F3600
m/s = 30 meters per sec
The relative speed when the two trains meet each other: 30 + 25 = 55 m/sec
:
"Calculate the time in seconds that it takes for the two trains to completely pass one another"
%28120%2B155%29%2F55 = 5 seconds