question_answer

35.      A river is flowing from west to east with a                speed of 5 m/min. A man can swim in still water with a velocity 10 m/min. In which direction should the man swim so, as to take the shortest possible path to go to the south?            

A) \[30{}^\circ \]east of south         

B)        \[60{}^\circ \] east- of south      

C)                        \[60{}^\circ \]west of south       

D)        \[30{}^\circ \]west of north

Correct Answer: A

Solution :

Let the swimmer swims at an angle\[\theta \]with the vertical. \[\therefore \]  \[\sin \theta =\frac{{{v}_{r}}}{{{v}_{s}}}=\frac{5}{10}=\frac{1}{2}=\sin 30{}^\circ \]     \[\theta =30{}^\circ \] The swimmer should swim 30° east of south to take the shortest possible path to go to the south.