Question

A person is swimming with a speed of $10$ $\text{m/s}$ at an angle of ${120}^{\circ }$ with the flow and reaches to a point directly opposite on the other side of the river. Then the speed of the flow is $x\text{m/s}$. The value $x$ to the nearest integer is.

Answer 1

Since the person reaches the directly opposite side of the river, its velocity along the river must be zero.


So, the component of speed of the swimmer along the river is equal to the speed of the river.

$10\sin {30}^{\circ }=V_R$

$\Rightarrow V_R=\frac{10}{2}=5\text{m/s}=x\text{m/s}$

$\therefore x=5$