A boat moves relative to water with a velocity which is `n=2.0` times less than the river flow velocity. At what angle to the stream direction must the boat move to minimize drifting?

Options

A. `45^(@)`
B. `60^(@)`
C. `120^(@)`
D. `90^(@)`

Answer

C

Explanation

`x=(v cos theta+v_(r))t_(0)`
`x=(v cos theta+v_(r))l/(v sin theta), Here v=v_(r)/2,v_(r)=2v`
`x=(v cos theta+2v)/(v sin theta)l=((cos theta+2)/(sin theta))l`
`x=(cot theta+2cosec theta)l` For minimum drifting `(dx)/(d theta)=0rArr theta=120^(@)`