Question

A string is wound round the rim of a mounted flywheel of mass $20kg$ and radius $20cm$. A steady pull of $25N$ is applied on the cord. Neglecting friction and mass of the string, the angular acceleration of the wheel is

• A. $50s^{-2}$
• B. $25s^{-2}$
• C. $12.5s^{-2}$
• D. $6.25s^{-2}$

Answer 1

Answer: (C)

The mass of flywheel $=20kg$
Radius $=20cm$
$=\frac{20}{100}m$
$=\frac{1}{5}m$
The moment of inertia $=\frac{1}{2}M{R}^2$
$=\frac{1}{2}\times 20\times {\left[\frac{1}{5}\right]}^2$
$I<0.4kg\cdot m^2$
Angular acceleration $\alpha =\frac{\tau }{I}$
$=\frac{FR}{I}$
$=\frac{25\times \frac{1}{5}}{0.4}$
$=12.5s^{-2}$