A ship is moving towards east at `10km*h^(-1)`. A boat is moving north of east making an angle of `30^@` with the north. What should be the velocity of the boat so that the boat always appears, from the ship , to move towards north ?

Explanation

Let the velocity of the ship be `vecu=vec(OA)` and velocity of the boat be `vecv=vec(OB)` [Fig.2.43]

Hence, the velocity of the boat with respect to the ship,
`vecw=vecv-vecu=vec(AB)`
From the figure,
`sin 30^@=u/v or, 1/2 =u/v`
or, `v=2u=2xx10km*h^(-1) =20km*h^(-1)` [Given , `u=10km*h^(-1)`]