25-08-2017, 09:32 PM
FORMULAS
Convert speed from km/hr to m/sec
a km/hr=[a*5/18]m/s
2. Convert speed from m/sec to km/hr
a m/s =[a*18/5]km/hr
3. Time taken by a train of length l meters to pass a pole or standing man or a signal post is equal to the time taken by the train to cover l meters.
4. Time taken by a train of length l meters to pass a stationery object of length b meters is the time taken by the train to cover (l + b) meters.
5. Suppose two trains or two objects bodies are moving in the same direction at u m/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 u m/s and v m/s, then their relative speed is = (u + v) m/s.
7. If two trains of length a meters and b meters are moving in opposite directions at u m/s and v m/s, then:
The time taken by the trains to cross each other
= (a+b)/(u+v) sec.
8. If two trains of length a meters and b meters are moving in the same direction at u m/s and v m/s, then:
The time taken by the faster train to cross the slower train
= (a+b)/(u-v) sec.
9. 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)