Question

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

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

Answer 1

Answer: (C)

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