Question

The amplitude and the periodic time of a S.H.M. are 5cm and 6sec respectively. At a distance of 2.5cm away from the mean position, the phase will be

• A. $5\pi/12$
• B. $\pi/4$
• C. $\pi/3$
• D. $\pi/6$

Answer 1

Answer: (D)

$\pi/6$

Answer 2

Equation of motion is $y = 5\sin\frac{2\pi t}{6}$. For $y = 2.5cm$

$2.5 = 5\sin\frac{2\pi t}{6}$ ⇒ $\frac{2\pi t}{6} = \frac{\pi}{6}$ ⇒ $t = \frac{1}{2}\sec$

and phase $= \frac{2\pi t}{6} = \frac{\pi}{6}$.