Formulae Essay

8689 WordsApr 28, 201235 Pages
http://123techbooks.blogspot.com/ 123techbooks@gmail.com IMPRTANT FORMULAS PROBLEMS ON TRAINS: 1. Speed, Time and Distance: Speed = Distance , Time = Distance , Distance = (Speed x Time). Time Speed 2. km/hr to m/sec conversion: x km/hr = x x 5 m/sec. 18 3. m/sec to km/hr conversion: x m/sec = x x 18 km/hr. 5 4. If the ratio of the speeds of A and B is a : b, then the ratio of the the times taken by then to cover the same distance is 1 : 1 or b : a. a b 5. Suppose a man covers a certain distance at x km/hr and an equal distance at ykm/hr. Then, the average speed during the whole journey is 2xy km/hr. x + y 1. km/hr to m/s conversion: a km/hr = a x 5 m/s. 18 2. m/s to km/hr conversion: a m/s = a x 18 km/hr. 5 3. Time taken by a train of length l metres to pass a pole or standing man or a signal post is equal to the time taken by the train to cover l metres. http://123techbooks.blogspot.com/ 123techbooks@gmail.com 4. Time taken by a train of length l metres to pass a stationery object of length bmetres is the time taken by the train to cover (l + b) metres. 5. Suppose two trains or two objects bodies are moving in the same direction at um/s and v m/s, where u > v, then their relative speed is = (u - v) m/s. 6. Suppose two trains or two objects bodies are moving in opposite directions at um/s and v m/s, then their relative speed is = (u + v) m/s. 7. If two trains of length a metres and b metres are moving in opposite directions atu m/s and v m/s, then: The time taken by the trains to cross each other = (a + b) sec. (u + v) 8. If two trains of length a metres and b metres are moving in the same direction atu m/s and v m/s, then: The time taken by the faster train to cross the slower train = (a + b) sec. (u - v) 9. If two trains (or bodies) start at the same time from points A and B towards each other and