A swimmer can swim with velocity of $12 \mathrm{~km} / \mathrm{h}$ in still water. Water flowing in

Question

A swimmer can swim with velocity of $12 \mathrm{~km} / \mathrm{h}$ in still water. Water flowing in a river has velocity $6 \mathrm{~km} / \mathrm{h}$. The direction with respect to the direction of flow of river water he should swim in order to reach the point on the other bank just opposite to his starting point is $\qquad$ ${ }^{\circ}$. (Round off to the nearest integer) (Find the angle in degrees)\

Professor PC Thomas Classes · Answer

(120) : Velocity of swimmer in still water, $v_{m}=12 \mathrm{~km} / \mathrm{h}$\ Velocity of water flowing, $v_{r}=6 \mathrm{~km} / \mathrm{h}$\ From diagram,\ $v_{m} \sin 	heta=v_{r}$\ $v_{m} \sin 	heta=6$\ $12 \sin 	heta=6$ or $\sin 	heta=\frac{1}{2} ; 	heta=\frac{\pi}{6}=30^{\circ}$\ $	herefore$ Direction with respect to flow of water $=90^{\circ}+30^{\circ}=120^{\circ}$\