Question

Answer these questions on the basis of given figure and information
A cord of negligible mass is wound round the rim of a fly wheel (disc) of mass 20 kg and radius 20 cm. A steady pull of $25\, N$ is applied on the cord as shown in figure. The flywheel is mounted on a horizontal axle with frictionless bearings

Compute the angular acceleration of the wheel

• A. $12.50 \,s^{-2}$
• B. $6\,s^{-2}$
• C. $10\, s^{-2}$
• D. $8 \, s^{-2}$

Answer 1

Answer: (A)

We use, $I \alpha=\tau$
The torque, $\tau= FR$
$=25 \times 0.20 N - m (\text { as } R =0.20 m )$
$=5.0 \,N - m$
$I = MOI$ of flywheel about its axis
$=\frac{M R^{2}}{2}=\frac{20.0 \times(0.2)^{2}}{2}$
$=0.4 kg - m ^{2}$
$\alpha=$ angular acceleration
$=5.0 N - m / 0.4 \,kg - m ^{2}=12.50 s ^{-2}$