Motion in a Plane - Result Question 59
62. A boat is sent across a river with a velocity of $8 km h^{-1}$. If the resultant velocity of boat is $10 km h^{-1}$, then the velocity of the river is
(a) $12.8 km h^{-1}$
(b) $6 km h^{-1}$
(c) $8 km h^{-1}$
(d) $10 km h^{-1}$
[1993]
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Solution:
- (b) $v_r=\sqrt{v_R^{2}-v_B^{2}}$
$=\sqrt{10^{2}-8^{2}}=6 kmh^{-1}$
