question_answer

A person aiming to reach the exactly opposite point on the bank of a stream is swimming with a speed of 0.5 m/s at an angle of \[120{}^\circ \] with the direction of flow of water. The speed of water in the stream is                                          [CBSE PMT 1999]

A)                 1 m/s    

B)                 0.5 m/s

C)                 0.25 m/s

D)                             0.433 m/s

Correct Answer: C

Solution :

                                \[\sin {{30}^{o}}=\frac{{{v}_{r}}}{{{v}_{m}}}\]\[=\,\frac{1}{2}\Rightarrow {{v}_{r}}=\frac{{{v}_{m}}}{2}\]=\[\frac{0.5}{2}\]\[=0.25\,m/s\]