Question

A uniform disc of mass `M` and radius `R` is mounted on an axle supported in frictionless bearings. A light cord is wrapped around the rim of the disc and a steady downward pull `T` is exerted on the cord. The angular acceleration of the disc is
A. `(T)/(MR)`
B. `(MR)/(T)`
C. `(2T)/(MR)`
D. `(MR)/(2 T)`

Answer 1

Correct Answer - C
( c) Torque exterted on the disc `tau = TR`
Now `tau = I prop`
or `prop = (tau)/(I) = (TR)/(1/(2) MR^2) =(2 TR)/(MR^2) = (2 T)/(MR)`.