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 $(\cos 0^{\circ}=1)$.
\(\omega \cos \phi\)
\(\mathrm{a} \omega\)
\(\omega \cos 2 \phi\)
\(-\mathrm{a} \omega \cos 2 \phi\)
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:
$a \omega$.