Question

A cord of negligible mass is wound around the rim of a flywheel (disc) of mass 20$kg$ and radius 20 $cm$. A steady pull of 25$N$ is applied on the cord as shown in the figure. Angular acceleration of flywheel is :

• A. $5rad/s^2$
• B. $12.5rad/s^2$
• C. $25rad/s^2$
• D. $10rad/s^2$

Answer 1

The correct option is B $12.5rad/s^2$

Given,

Mass of the wheel $M=20kg$

Radius of the wheel $R=20cm=0.2m$

Force, $F=25N$

Length $l=2m$

torque ,$\tau =Id$

or,

$\begin{array}{c}F\times R=\frac{M{R}^2}{2}d\\ \therefore \alpha =\frac{2F}{MR}=\frac{2\times 25}{20\times 0.2}\\ =12.5rad/s^2\end{array}$

Hence Option $B$ is correct .