Question

A river is flowing from W to E with a speed of $5\frac{m}{min}$. A man can swim in still water with a velocity 10 $\frac{m}{min}$. In which direction should the man swim so as to take the shortest possible path to go to the south.

• A. with downstream
• B. with downstream
• C. with downstream
• D.

Answer 1

The correct option is C with downstream

For shortest possible path man should swim with an angle $(90+\theta )$ with downstream.
From the fig, $\sin \theta =\frac{v_r}{v_m}=\frac{5}{10}=\frac{1}{2}\Rightarrow \therefore \theta ={30}^{\circ }$
So angle with downstream = ${90}^{\circ }+{30}^{\circ }={120}^{\circ }$