Buses A and B are moving in the same direction with speed `20 ms^(-1)` and `15 ms^(-1)` respectively. Find the relative velcoity of A w.r.t. B and relative velocity of B w.r.t. A.

Explanation

Let their direction of motion of bus A is `hati` then `vecv_(A)=(20m//s)hati`
(a) Relative velocity of A w.r.t. B `=vecv_(AB)=vecV_(A)-vecv_(B)=` (actual velocity of A)-(velocity of B)
`=(20 m//s)hati-(15m//s)hati=5m//shati`
i.e. A is moving with speed `5m//s` w.r.t B in `hati` direction.
(b) Relative velocity of B w.r.t `A=vecv_(BA)=vecv_(B)-vecv_(A)=` (Actual velocity of B)-(velocity of A)
`=(15m//s)hati-(20 m//s)hati=(-5m//s)hati=(5m//s)(-hati)`
i.e. B moving in `-hati` direction w.r.t A, at speed 5 m/s