Question

A river is flowing from west to east at a speed of $5\text{m/min}$. A man on the south bank of the river, capable of swimming at $10\text{m/min}$ in still water, wants to swim across the river in the shortest time. He should swim in a direction

• A. due north
• B. ${30}^{\circ }$ east of north
• C. ${30}^{\circ }$ west of north
• D. ${60}^{\circ }$ east of north

Answer 1

The correct option is A due north

${\overrightarrow{V}}_{SR}+{\overrightarrow{V}}_{RG}={\overrightarrow{V}}_{SG}$
For minimum time, the swimmer should swim perpendicular to the direction of river flow. So, he should swim due north.