Q 11-03-030NEETJEE MainMedium
A boat whose speed in still water is $5$ m/s must reach the point directly opposite on the other bank of a river flowing at $3$ m/s. The angle between the boat's heading and the direction of the river flow must be
Answer: (C) $127°$
The upstream component of the boat's velocity must cancel the river: $5\sin\alpha = 3$, where $\alpha$ is measured from the perpendicular to the banks. So $\alpha = 37°$ upstream of the perpendicular.
Angle with the direction of flow $= 90° + 37° = 127°$.
Solution by Sreeraj P, M.Sc Physics