Speed, Time and Distance
- Two trains 125 metres and 115 metres in length, are running towards each other on parallel lines, one at the rate of 33 km/hr and the other at 39 km/hr. How much time (in seconds) will they take to pass each other from the moment they meet ?
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Relative speed
= (33 + 39) kmph
= 72 kmph= 72 × 5 m/sec. 18
= 20 m/sec.∴ Time taken in crossing = Length of both trains Relative speed = 125 + 115 = 240 20 20
= 12 secondsCorrect Option: C
Relative speed
= (33 + 39) kmph
= 72 kmph= 72 × 5 m/sec. 18
= 20 m/sec.∴ Time taken in crossing = Length of both trains Relative speed = 125 + 115 = 240 20 20
= 12 seconds
- A goods train starts running from a place at 1 P.M. at the rate of 18 km/hour. Another goods train starts from the same place at 3 P.M. in the same direction and overtakes the first train at 9 P.M. The speed of the second train in km/hr is
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Distance covered by the first goods train in 8 hours = Distance covered by the second goods train in 6 hours.
⇒ 18 × 8 = 6 × x⇒ x = 18 × 8 = 24 kmph 6 Correct Option: A
Distance covered by the first goods train in 8 hours = Distance covered by the second goods train in 6 hours.
⇒ 18 × 8 = 6 × x⇒ x = 18 × 8 = 24 kmph 6
- Two trains, 80 metres and 120 metres long, are running at the speed of 25 km/hr and 35 km/hr respectively in the same direction on parallel tracks. How many seconds will they take to pass each other ?
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Relative speed = 35 – 25 = 10 kmph
= 10 × 5 m/sec. 18
Total length = 80 + 120 = 200 metres∴ Required time = Sum of the lengths of trains Relative speed = 200 10 × 5 18 = 200 × 18 = 72 seconds 10 × 5 Correct Option: D
Relative speed = 35 – 25 = 10 kmph
= 10 × 5 m/sec. 18
Total length = 80 + 120 = 200 metres∴ Required time = Sum of the lengths of trains Relative speed = 200 10 × 5 18 = 200 × 18 = 72 seconds 10 × 5
- Two trains, of same length, are running on parallel tracks in the same direction with speed 60 km/hour and 90 km/hour respectively. The latter completely crosses the former in 30 seconds. The length of each train (in metres) is
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When two trains cross each other, they cover distance equal to the sum of their length with relative speed.
Let length of each train = x metre
Relative speed = 90 – 60
= 30 kmph= 30 × 5 m/sec. 18 = 25 m/sec. 3 ∴ 2x = 30 25 3 ⇒ 2x = 30 × 25 3
⇒ 2x = 250
⇒ x = 125 metresCorrect Option: A
When two trains cross each other, they cover distance equal to the sum of their length with relative speed.
Let length of each train = x metre
Relative speed = 90 – 60
= 30 kmph= 30 × 5 m/sec. 18 = 25 m/sec. 3 ∴ 2x = 30 25 3 ⇒ 2x = 30 × 25 3
⇒ 2x = 250
⇒ x = 125 metres
- Two trains 180 metres and 120 metres in length are running towards each other on parallel tracks, one at the rate 65 km/hour and another at 55 km/hour. In how many seconds will they be clear of each other from the moment they meet ?
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Required time = Sum of the lengths of trains Relative speed
Relative speed = 65 + 55
= 120 kmphRequired time = 180 + 120 120 × 5 18 = 300 × 18 = 9 seconds 120 × 5 Correct Option: B
Required time = Sum of the lengths of trains Relative speed
Relative speed = 65 + 55
= 120 kmphRequired time = 180 + 120 120 × 5 18 = 300 × 18 = 9 seconds 120 × 5