A solid cylinder of mass 2 k g and radius 4 c m is rotating about its axis at the rate of 3 rpm . The torque…

A solid cylinder of mass 2 kg and radius 4 cm is rotating about its axis at the rate of 3 rpm. The torque required to stop after 2π revolutions is
  1. 2×10-6 N m
  2. 2×10-3 N m
  3. 12×10-4 N m
  4. 2×106 N m

Solution

From rotational kinematic equations,
ωf2-ωi2=2αθ
02-3 2π602=2 α 2π2π
α=-1800 rad s-2
∴ Torque required τ=Iα
=24×10-222×1800
=16×10-4800
=2×10-6 N m ~

Asked in: NEET 2019 (All India)

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