Question

A swimmer crosses a river of width d flowing at velocity v. While swimming, he keeps himself always at an angle of 120° with the river flow and on reaching the other end he finds a drift of d/2 in the direction of flow of river. The speed of the swimmer with respect to the river is

• A. (2 –$\sqrt{3}$) v
• B. 2 (2 –$\sqrt{3}$) v
• C. 4 (2 –$\sqrt{3}$) v
• D. (2 +$\sqrt{3}$) v

Answer 1

Answer: (C)

4 (2 –$\sqrt{3}$) v

Answer 2

Drift = d/2 = (V_r – V_ssin30)d/V_scos30

⇒ V_s = 4 (2 – $\sqrt{3}$)V,

Hence (3) is correct.