**3)**. Time taken by a train of length

**l**meters to pass a pole or a 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 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 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).**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)