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JEE Main 2011 (AIEEE) · Rotational Kinematics & Dynamics

Rotational Kinematics & Dynamics question from JEE Main 2011 (AIEEE)

Q73JEE Main 2011 · AIEEEMedium

Rotational Kinematics & Dynamics

A mass mm hangs with the help of a string wrapped around a pulley on a frictionless bearing. The pulley has mass mm and radius R.R. Assuming pulley to be a perfect uniform circular disc, the acceleration of the mass m,m, if the string does not slip on the pulley, is:

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Answer: (b)

  1. Disc pulley: I=12mR2I = \frac{1}{2}mR^2, so T=IaR2=ma2T = \frac{Ia}{R^2} = \frac{ma}{2}.
  2. Block: mg−ma2=ma⇒a=2g3mg - \frac{ma}{2} = ma \Rightarrow a = \frac{2g}{3}
  3. So the answer is (b) 23g\frac{2}{3}g.
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