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JEE Main 2014 (19 Apr, Shift 1) · Rolling Motion

Rolling Motion question from JEE Main 2014 (19 Apr, Shift 1)

Q78JEE Main 2014 · 19 APR · SHIFT 1Difficult

Rolling Motion

Consider a cylinder of mass M resting on a rough horizontal rug that is pulled out from under it with acceleration 'a' perpendicular to the axis of the cylinder. What is Ffriction at point P? It is assumed that the cylinder does not slip.

Figure

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Answer: (d)

  1. Friction ff on the cylinder points along aa: centre acceleration ac=fMa_c = \dfrac{f}{M}.
  2. Torque: fR=12MR2α⇒αR=2fMfR = \frac{1}{2}MR^2\alpha \Rightarrow \alpha R = \dfrac{2f}{M}.
  3. No slipping: acceleration of P equals the rug's, ac+αR=a⇒3fM=aa_c + \alpha R = a \Rightarrow \dfrac{3f}{M} = a.
  4. f=Ma3f = \dfrac{Ma}{3}, so the answer is (d).
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