The displacement of a particle executing S.H.M. is $x=a \sin (\omega t-\phi)$. Velocity of the particle at…

The displacement of a particle executing S.H.M. is $x=a \sin (\omega t-\phi)$. Velocity of the particle at time $t=\frac{\phi}{\omega}$ is $(\cos 0^{\circ}=1)$.
  1. \(\omega \cos \phi\)
  2. \(\mathrm{a} \omega\)
  3. \(\omega \cos 2 \phi\)
  4. \(-\mathrm{a} \omega \cos 2 \phi\)

Solution

$x=a \sin (\omega t-\phi)$ The velocity $v$ is the first derivative of displacement $x$ with time $t$ : $v=\frac{d x}{d t}$ Let's compute the derivative: $\begin{aligned} & v=\frac{d}{d t}[a \sin (\omega t-\phi)] \\ & v=a \cos (\omega t-\phi) \cdot \frac{d}{d t}(\omega t-\phi) \\ & v=a \cos (\omega t-\phi) \cdot \omega \\ & v=a \omega \cos (\omega t-\phi) \end{aligned}$ We need to calculate this velocity at time $t=\frac{\phi}{\omega}$ : $\begin{aligned} & v=a \omega \cos \left(\omega \cdot \frac{\phi}{\omega}-\phi\right) \\ & v=a \omega \cos (\phi-\phi) \\ & v=a \omega \cos \left(0\right) \\ & v=a \omega \cdot 1 \\ & v=a \omega \end{aligned}$ Therefore, the correct answer is Option B: $a \omega$.

Asked in: MHT CET 2022 (06 Aug Shift 2)

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