Motion in a Plane - Result Question 55

58. A person swims in a river aiming to reach exactly opposite point on the bank of a river. His speed of swimming is $0.5 m / s$ at an angle $120^{\circ}$ with the direction of flow of water. The speed of water in stream is

[1999]

(a) $1.0 m / s$

(b) $0.5 m / s$

(c) $0.25 m / s$

(d) $0.43 m / s$.

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Answer:

Correct Answer: 58. (c)

Solution:

  1. (c)

Velocity of person, $ \vec{v} _m=0.5 m / s$

$ \begin{aligned} & \sin 30^{\circ}=\frac{v_w}{v_m} \Rightarrow v_w=v_m \sin 30^{\circ} \\ & \Rightarrow v_w=\frac{v_m}{2}=\frac{0.5 m / s}{2}=0.25 m / s \end{aligned} $