3. Time taken by a train of length 1 metres to pass a pole or a standing man or a signal
post is equal to the time taken by the train to cover 1 metres.

4. Time taken by a train of length 1 metres to pass a stationary object of length
b metres is the time taken by the train to cover (I + b) metres.

5. Suppose two trains or two bodies are moving in the same direction at u m / s and
y m / s, where u > y, then their relatives speed = (u - y) m/ s.

6. Suppose two trains or two bodies are moving,in opposite directions at u m / s and
y m / s, then their relative speed is = (u + y) m/s.

7. If two trains of length a metreS and b metres are moving in opposite directions at
u m/s and y m/s, then 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
at u m/s and y 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 after crossing they take a and b sec in reaching B and A respectively, then
(A's speed) : (B's speed) = ( √a : √b )