Question

A disc initially at rest, is rotated about its axis with uniform angular acceleration. In the first $2 \, s,$ it rotates an angle $\theta $ . In the next $2 \, s$ , the disc rotates through an angle

• A. $\theta $
• B. $2\theta $
• C. $3\theta $
• D. $4\theta $

Answer 1

Answer: (C)

Because of uniform angular acceleration. we can use the equation of motion in rotation
$\theta =\frac{1}{2} \, \alpha \, \left(2\right)^{2} $$\left[\omega_0=0\right]$
$\theta =2\alpha $
And
$\theta +\theta '=\frac{1}{2}\alpha \, \left(2 + 2\right)^{2} $$\left[\because \omega_0=0\right]$
$\theta +\theta '=8\alpha $
Hence, $\theta '=3\theta $