Question

A river is flowing from West to East at a speed of $5m$ per min. If a swimmer standing on South bank of the river wants to swim across the river in the shortest time, then he should swim in a direction (speed of swimmer in still water)

• A. ${30}^o$ East-North
• B. Due North
• C. ${30}^o$ West-North
• D. ${60}^o$ East-North

Answer 1

Answer: (B)

Due North

The given condition can be shown as infigure
Time taken to cross the river, $t=\frac{d}{V_S\cos \theta }$
for time to be minimum, $\cos \theta =$ maximum
$\Rightarrow \theta =0^o$
So, summer should swim due North.