1) A disc has mass 'M' and radius 'R'. How much tangential force should be applied to the rim of the disc, so as to rotate with angular velocity 'ω ' in time 't'? A) MRω4t B) MRω2t C) MRωt D) MRωt Answer: Option BExplanation: Given, mass of disc= M Radius of disc= R we know that, τ=lα But , τ=F×R ∴ l=MR22 and α=ωt therefore , F x R= MR22×ωt F= MRω2t