Distance & Time Conversions to remember:
1 km = 1000 meters
1 hour = 60 mins = 3600 sec
1 meter = 100 cms
1 mile = 1760 yards
1 yard = 3 feet
1 mile = 5280 feet
1 mph(miles per hour) = 1 * 1760 /1 * 3600 = 22/45 yards/sec
1 mph(miles per hour) = 1 * 5280/1* 3600 = 22/15 feet/sec
1 mile = 1.609 km = 1609 meters (for calulation purpose, value of mile can be approximated to 1600 meters)
Kilometer/hour(km/hr) to Meter/Second(m/s) conversion:
a km/hr = a * 5/18 m/s
Meter/Second(m/s) to Kilometer/hour(km/hr) conversion:
a m/s = a * 18/5 km/hr
Formulae:
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.
Time taken by a train of length l metres to pass a stationery object of length x metres is the time taken by the train to cover (l + x) metres.
Suppose two trains or two objects bodies are moving in the same direction at x m/s and y m/s, where x > y, then their relative speed is = (x - y) m/s.
Suppose two trains or two objects bodies are moving in opposite directions at x m/s and y m/s, then their relative speed is = (x + y) m/s.
If two trains of length a metres and b metres are moving in opposite directions at x m/s and y m/s, then:
The time taken by the trains to cross each other = (a + b)/(x + y) sec
If two trains of length a metres and b metres are moving in the same direction at x m/s and y m/s, then:
The time taken by the faster train to cross the slower train = (a + b)/(x - y) sec.
If two trains (or bodies) start at the same time from points A and B towards each other and after crossing they take a and b sec in reaching B and A respectively, then:
(A's speed) : (B's speed) = (b : a)
|
