Q. A boat is sent across a river with a velocity of boat is $10\ km/hr$. If the resultant velocity of boat is $10\ km/hr,$ then velocity of the river is :
A) $10\ km/\ hr$
B) $8\ km/hr$
C) $6\ km/hr$
D) $4\ km/hr$
Explanation
(c) Given $\overrightarrow{AB} =$ Velocity of boat $= km/hr$
$\overrightarrow{AC} =$ Resultant velocity of boat $= 10\ km/hr$
$\overrightarrow{BC} =$ Velocity of river
$= \sqrt{AC^{2} - AB^{2}}$
$= \sqrt{(10)^{2} - (8)^{2}} = 6\ km/hr$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.