# PROBLEMS ON TRAINS ->IMPORTANT FORMULA

1. a km/hr = [a * 5/18]m/s.
2. a m/s = [a * 18/5] km/hr.
3. Time taken by a train of length l metres to pass a pole or a
standing man or a signal post is equal to the time taken by the train
to cover l metres.
4. Time taken by a train of length l metres to pass a stationary
object of length b metres is the time taken by the train to cover (l +
b) metres.
5. 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 relatives speed
= (u – v) m/s.
6. Suppose two trains or two 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 metres and b metres are moving in
opposite directions at u
8. If two trains of length a metres and b metres 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. a km/hr = [a * 5/18]m/s.
a m/s = [a * 18/5] km/hr.
Time taken by a train of length l metres to pass a pole or a
standing man or a signal post is equal to the time taken by the train to cover l metres.
10. Time taken by a train of length l metres to pass a stationary
object of length b metres is the time taken by the train to cover (l + b) metres.
11. 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 relatives speed
= (u – v) m/s.
12. Suppose two trains or two bodies are moving in opposite
directions at u m/s and v m/s, then their relative speed is = (u + v) m/s
13. If two trains of length a metres and b metres are moving in
opposite directions at u If two trains of length a metres and b metres 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.
14. 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)