In a Laboratory Experiment, a Student Brings Up the Rotational $0.0850 \mathrm {~kg} \cdot \mathrm { m } ^ { 2 }$

Multiple Choice

In a laboratory experiment, a student brings up the rotational speed of a flywheel to 30.0 rpm. She then allows it to slow down on its own, and counts 240 revolutions before the apparatus uniformly comes to a stop. The moment of inertia of the flywheel is $0.0850 \mathrm {~kg} \cdot \mathrm { m } ^ { 2 }$
What is the magnitude of the retarding torque on the flywheel?

A) $0.159 \mathrm {~N} \cdot \mathrm { m }$
B) $0.0000136 \mathrm {~N} \cdot \mathrm { m }$
C) $0.0787 \mathrm {~N} \cdot \mathrm { m }$
D) $0.000278 \mathrm {~N} \cdot \mathrm { m }$
E) $0.0425 \mathrm {~N} \cdot \mathrm { m }$