Question

A man who can swim at the rate of $2km/hr$ (in still river) cross a river to a point exactly opposite on the other bank by swimming in a direction of ${120}^o$ to the flow of the water in the river. The velocity of the water current in $km/h$ is

• A. $1$
• B. $2$
• C. $1/2$
• D. $3/2$

Answer 1

The correct option is A $1$

$V_m$= Velocity of man,

$V_r$= Velocity of rain,

$V_{mr}=V_m-V_r$

Taking components,

$V_{mr}\cos {120}^{\circ }=V_m\cos {90}^{\circ }-V_r\cos 0^{\circ }$

$2\times \left(-\frac{1}{2}\right)=-V_r$

So,$V_r=1km/hr$