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- Speed = Distance/Time
- Time = Distance /Speed
- Distance = Speed x Time
- km/hr to m/s conversion:1 kmph = 5/18 m/s m/s to km/hr conversion: 1 m/s = 18/5 m/s
- . If the ratio of speeds of train A and B is a : b, then the ratio of time taken by them to cover the same distance = b : a.
- If a man covers a certain distance at x km/hr and an equal distance at y km/hr. Then,the average speed during the whole journey is 2xy/(x + y) km/h
- 8. The time taken by a train in passing a pole or standing man is the same as the time taken by the train to cover a distance equal to its own length.
- 9. The time taken by a train of length ‘L’ metres in passing a stationary object of length ‘B’ metres is equal to the time taken by the train to cover a distance equal to (L + B) m.
- 10. If two trains are moving in the same directions at u m/s and v m/s, where u > v, then their relative speed will be equal to the difference of their speeds i.e. (u – v) m/s.
- 11. If two trains are moving in the opposite directions at u m/s and v m/s, then their relative speed will be equal to the sum of their speeds i.e. (u + v) m/s.
- 12.If two trains of length ‘a’ metres and ‘b’ metres are moving in the same directions at u m/s and v m/s respectively, then:
- The time taken by the faster train to cross the slower train is
- (a + b)/(u – v) sec.
- 13.If two trains of length ‘a’ metres and ‘b’ metres are moving in the opposite directions at u m/s and v m/s respectively, then:
- The time taken by the faster train to cross the slower train is
- (a + b)/(u + v) sec.
- 14.If two trains start at the same time from points A and B towards each other and after crossing they take ‘a’ and ‘b’ hour in reaching B and A respectively, then:
- (A’s speed) : (B’s speed) = under root(b) : (underroot)a