Man A is sitting in a car moving with a speed of 54 `(km)/(hr)` observes a man B in front of the car crossing perpendicularly a road of width 15 m in three seconds. Then the velocity of man B (in `(m)/(s)`) will be:

Options

A. `5sqrt(10)` towards the carm at some angle
B. `5sqrt(10)` away from the car at some angle
C. `5` perpendicular to the road
D. `15` along the road

Answer

B

Explanation

Velocity of `A` and velocity of `B` relative to `A` are as shown
`:. Vec(V)_(B) = vec(V)_(BA) + vec(V)_(A)`
`rArr V_(0)=sqrt(5^(2)+15^(2))=5 sqrt(10)`

and direction of `vec(V)_(B)` is away from `vec(V)_(B)`.