question_answer

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:                                                [Pb. PET 2004]

A)                10 km/hr                          

B)                8 km/hr         

C)                6 km/hr                   

D)                           4 km/hr

Correct Answer: C

Solution :

                Given \[\overrightarrow{AB}=\]Velocity of boat= 8 km/hr               \[\overrightarrow{AC}=\]Resultant velocity of boat = 10 km/hr                                                                       \[\overrightarrow{BC}=\]Velocity of river\[=\sqrt{A{{C}^{2}}-A{{B}^{2}}}\]               \[=\sqrt{{{(10)}^{2}}-{{(8)}^{2}}}=6\ km/hr\]