Question

A boat is sent across a river with a velocity of $8$ km/hr. If the resultant velocity of boat is $10$ km/hr, then velocity of the river is

• A. $10km/hr$
• B. $8km/hr$
• C. $6km/hr$
• D. $4km/hr$

Answer 1

The correct option is C $6km/hr$

The Velocity of the boat is $8km/h$

Resultant velocity $=10km/h$

Let $V_{RB}$ is the resultant velocity of the boat with the river $V_B$ is the velocity of the boat $V_R$ is the velocity of the river,

So, $V_{RB}=\sqrt{V_R^2+V_B^2}$

$V_R^2=V_{AB}^2-V_B^2={10}^2-8^2=36$

$\Rightarrow V_R=6km/h$