Rule : When two trains are moving in opposite diections, then relatve speed will be the addition of their individiual speeds.
Rule : When two trains are moving in same diection, then relatve speed will be the subtrction of their individiual speeds.
Rule : On passing a platform by a certain train the net distance travelled is the sum of length of train and the length of platform both.
Rule : When a train passes through a pole or person standing, net distance travelled to pass is the length of the train
Ex. A train 120 m long is running at the speed of 54 km /hr. Find the time taken it to pass a man standing near the railway track.
Solution : speed of train = [54 * ( 5 / 18 ) ] = 15 m / sec
length of train = 120 m , So required time :
Ex. A train is moving at a speed of 54 km / hr. If the length of the train is 100 meters, how long will it take to cross a railway platform 110 meters long ?
Solution : speed of train = [54 * ( 5 / 18 ) ] = 15 m / sec
Distance covered in passing the platform = 100 + 110 = 210 m
Ex. Two trains 125 m and 100 m in length respectively are running in opposite directions, one at the rate of 50 km / hr and the other at the rate of 40 km /hr. At what time they will clear each other from the moment they meet ?
Solution : Relative speed of trains = (50 + 40) km / hr = [90 * ( 5 / 18 ) ] = 25 m / sec
Total length to be travelled = 125 + 100 = 225 m
Ex. Two trains 110 m and 100 m in length respectively are running in same directions, one at the rate of 100 km / hr and the other at the rate of 64 km / hr. At what time faster train will clear other train from the moment they meet ?
Solution : Since trains are running in same direction, so relative speed = 100-64 = 36 km / hr = [ 36 * ( 5 / 18 )] = 10 m / sec
Total length to be travelled = 110 + 100 = 210 m
Ex. A train 125 m in length, moves at a speed of 82 km / hr , In what time the train will cross a boy who is walking at 8 km / hr in opposite direction ?
Solution : Relative speed = 82+8 = 90 km / hr = [ 90 * ( 5 / 18 )] = 25 m / sec
Ex. A train passes a standing pole on the platform in 5 seconds and passes the platform completely in 20 seconds. If the length of the platform is 225 meters. Then find the length of the train ?
Solution : Let the length of the train is x meter
So speed of train =( x / 5 ) m / sec
Also speed of train = ( 225 + x ) / 20 m/sec
Ex. Two trains of length 115 m and 110 m respectively run on parallel rails. When running in the same direction the faster train passes the slower one in 25 seconds, but when they are running in opposite directions with the same speeds as earlier, they pass each other in 5 seconds. Find the speed of each train ?
Solution :
Let the speed of trains be x m/sec and y m/sec espectively.
When they move in same direction their relative speed is : x - y
When they moves in opposite direction their relative speed is : x + y
On solving two equations x=27 m/s and y=18 m/sec
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