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

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3-1.Vectors

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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 ........$km/hr$

A

$10$

B

$8 $

C

$6$

D

$4$

Solution

(c) 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$

Standard 11

Physics

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