Question

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

• A. $1.0\, m/s$
• B. $0.5\, m/s$
• C. $0.25\, m/s$
• D. $0.43\, m/s$

Answer 1

Answer: (C)

$0.25\, m/s$

Answer 2

Let the speed of water $=\overrightarrow{u}$
Speed of swimmer $=\overrightarrow{v}=0.5\,m/sec$
Angle between $=\overrightarrow{v}$ and $=\overrightarrow{u}$ is $120^?$. Then
$sin\,\theta=\frac{\vec{u}}{\vec{v}} \Rightarrow \frac{u}{0.5}=\frac{1}{2} or u=0.25\,ms^{-1}$