A rod AB, 10 feet long moves with its ends A and B on two perpendicular OX and OY respectively when A is 8 feet from 0, it is moving away at the rate of 2 feet/sec. At this instant B is moving at the rate.
Answer & explanation
Correct answer: option 3
OB = 6
$OA^2+OB^2=100$
$⇒2×OA\frac{d(OA)}{dt}+2×OB\frac{d(OB)}{dt}=0$
$⇒OA.V_A+OB.V_B=0$
$⇒V_B=-\frac{2×8}{6}=-\frac{8}{3}$ feet/s