A disc of mass $$4$$ kg and radius $$50$$ cm is rotating with angular velocity $$30$$ $$rad/s$$ about a spindle passing through its centre and perpendicular to the plane of the disc. A constant braking torque is applied on the disc and the disc stops spinning in $$10$$ second. Then the magnitude of the braking torque is

Question

Infinity Learn · Accepted Answer

Moment of inertia $$I=12$$×$$4$$×$$0.52Kg$$−$$m2=0.5$$ kg−$$m2using$$ ω$$=$$ω$$0$$−αt⇒$$0=30$$−α×$$10$$⇒α$$=3$$ $$rad/s2$$∴ Braking torque τ$$=I$$α$$=0.5$$×$$3$$ N−$$m=1.5$$ N−m

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