A is a point on the circle with radius 8 and centre at $O$. A particle P is moving on the circumference of…

A is a point on the circle with radius 8 and centre at $O$. A particle P is moving on the circumference of the circle starting from A. M. is the foot of the perpendicular from $P$ on $O A$ and $\angle \mathrm{POM}=\theta$. When $O M=4$ and $\frac{d \theta}{d t}=6$ radians $/ \mathrm{sec}$, then the rate of change of PM is (in units/sec)
  1. $24 \sqrt{3}$
  2. 24
  3. $15 \sqrt{3}$
  4. $48 \sqrt{3}$

Solution

When $O M=4 \Rightarrow \cos \theta=\frac{O M}{O P}=\frac{1}{2}$
$\begin{aligned} & \text { Now, } P M=O P \sin \theta \Rightarrow P M=8 \sin \theta \\ & \Rightarrow \frac{d(P M)}{d t}=8 \cos \theta \frac{d \theta}{d t} \\ & \Rightarrow 8 \times \frac{1}{2} \times 6=24\end{aligned}$

Asked in: AP EAMCET 2024 (23 May Shift 1)

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