Two trains crossing each other in 14 sec when they are

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Two trains crossing each other in 14 sec when they are

Two trains cross each other in 14 sec when they are moving in the opposite direction, and when they are moving in the same direction they cross each other in 3 minute2 sec. Find the speed of the faster train by what percent more than the speed of the slower train?

Here we will learn about the concept of two trains passes in the opposite direction.

When two train passes a moving object (having some length) in the opposite direction

Let length of faster train be l meters and length of slower train be m meters

Let the speed of faster train be x km/hr

Relative speed = (x + y) km/hr.

Then, time taken by the faster train to pass the slower train = (l + m) meters/(x + y) km/hr

Now we will learn to calculate when two trains running on parallel tracks (having some length) in the opposite direction.               

Solved examples when two trains passes (having some length) in the opposite direction:

1. Two trains of length 150 m and 170 m respectively are running at the speed of 40 km/hr and 32 km/hr on parallel tracks in opposite directions. In what time will they cross each other?

Solution:            

Relative speed of train = (40 + 32) km/hr

                               = 72 km/hr

                               = 72 × 5/18 m/sec

                               = 20 m/sec

Time taken by the two trains to cross each other = sum of length of trains/relative speed of trains

                                                                   = (150 + 170)/20 sec

                                                                   = 320/20 sec

                                                                   = 16 sec

Therefore, the two trains crossed each other in 16 seconds.

2. Two trains 163 m and 187 m long are running on parallel tracks in the opposite directions with a speed of 47 km/hr and 43 km/hr in. How long will it take to cross each other?

Solution:            

Relative speed of train = (47 + 43) km/hr

                               = 90 km/hr

                               = 90 × 5/18 m/sec

                               = 25 m/sec

Time taken by the two trains to cross each other = sum of length of trains/relative speed of trains

                                                                   = (163 + 187)/25 sec

                                                                   = 350/25 sec

                                                                   = 14 sec

Therefore, the two trains crossed each other in 14 seconds.

Speed of Train

Relationship between Speed, Distance and Time

Conversion of Units of Speed

Problems on Calculating Speed

Problems on Calculating Distance

Problems on Calculating Time

Two Objects Move in Same Direction

Two Objects Move in Opposite Direction

Train Passes a Moving Object in the Same Direction

Train Passes a Moving Object in the Opposite Direction

Train Passes through a Pole

Train Passes through a Bridge

Two Trains Passes in the Same Direction

Two Trains Passes in the Opposite Direction

8th Grade Math Practice

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Concept:

When a train of length ‘l1’ metres running with speed ‘s1’ km/hr crosses another train of length ‘l2’ running with a speed of ‘s2’ in opposite direction in ‘t’ seconds :

(l1 + l2) = (s1 + s2) × t

When a train of length ‘l1’ metres running with speed ‘s’ km/hr crosses a bridge or a platform of length ‘l2’ in ‘t’ seconds:

(l1 + l2) = s × t × (5/18)

Calculations:

Let the length of first train be l1

Speed of first train be s1 = 5x

Length pf second train be l2

Speed of second train be s2 = 2x

(l1 + l2) = (s1 + s2) × t

⇒ (l1 + l2) = (5x + 3x) × 14 = 112x        ----(i)

Now the faster train crosses the platform of 190 m in 20 sec

⇒ (l1 + 190)/5x = 20

⇒ (l1 + 190) = 100x

⇒ l1 = 100x – 190

The slower train crosses a 290 m long platform in 36 sec

⇒ (l2 + 290)/3x = 36

⇒ (l2 + 290) = 108x

⇒ l2 = 108x – 290

∴ l1 + l2 = 100x – 190 + 108x – 290 = 208x – 480        ----(ii)

Equating (i) and (ii)

⇒ 208x – 480 = 112x

⇒ 96x = 480

⇒ x = 5

∴ s1 = 5 × 5 = 25 m/s, s2 = 3 × 5 = 15 m/s

l1 = 500 – 190 = 310, l2 = 540 – 290 = 250

∴ Time taken by both the trains to cross each other when they are 240 m apart

⇒ (l1 + l2 + 240)/(s1 + s2) = t

⇒ (310 + 250 + 240)/(25 + 15) = t

⇒ 800/40 = 20 sec

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