Question

The equation describing the motion of a simple harmonic oscillator along the $x$ axis is given as $x=A \cos (\omega t+\phi)$. If at time $t=0$, the oscillator is at $x=0$ and moving in the negative $x$-direction, then the phase angle $\phi$ is

• A. $ \frac{\pi }{2} $
• B. $ -\frac{\pi }{2} $
• C. $ \pi $
• D. $ 0 $

Answer 1

Answer: (A)

$x=A \,\,\,\cos (\omega t+\phi)$
Let $t=0$
$x=0$
$0=\cos \phi$
$\cos \frac{\pi}{2}=\cos \phi$
$\theta=\frac{\pi}{2}$