A uniform disk of mass and radius is initially at rest

PHYSICS · Single correct · CBSE · Physics · System of Particles and Rotational Motion · System of Particles and Rotational Motion

Problem

A uniform disk of mass

3.0\,\text{kg}

and radius

0.20\,\text{m}

is initially at rest. A motor applies a constant torque

\tau_m

to the disk for

4.0\,\text{s}

. Immediately afterward the motor is turned off, and the only torque acting is a constant

0.50\,\text{N}\,\text{m}

frictional torque opposite the rotation. The disk comes to rest

10\,\text{s}

after the motor is turned off. What is the magnitude of

\tau_m

? (a)

0.75\,\text{N}\,\text{m}

(b)

1.75\,\text{N}\,\text{m}

(c)

1.25\,\text{N}\,\text{m}

(d)

0.50\,\text{N}\,\text{m}