# Time Distance and Speed

- Formula to convert km/hr to meter per second.

a km/hr = [a* (5/18)] m/s

- Formula to convert km/hr to meter per second.

a m/s = [a* (18/5)] km/hr

- Time taken by train of length L meters to pass a stationary object of length b meters is the time taken by the train to cover (L+ b) meters.
- 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.
- Time taken by train of length L meters to pass a pole or a standing man or a single post is equal to the time taken by the train to cover L meters.
- Suppose two trains or two bodies are moving in opposite directions at u m / s and v m / s, then their relative speed = (u - v) m / s.
- 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)
^{1/2}: (a)^{1/2} - If two trains of length a meters and b meters are moving in opposite directions at u m / s and v m / s, then time taken by the trains to cross each other = (a+b)/(u+v)sec.
- Suppose two trains or two bodies are moving in the same direction at u m / s and v m / s, where u > v, then their relative speed = (u - v) m / s.