Q116 / 150 · MHT CET 2017 · Physics

A Wheel of moment of inertia 2 kg m2 is rotating about an axis passing through centre and perpendicular to its plane at a speed 60 rad s-1. Due to friction, it comes to rest in 5 minutes. The angular momentum of the wheel three minutes before it stops rotating is

  • A
    24  kg m2/s
  • B
    48 kg m2/s
  • Correct answer
    C
    72 kg m2/s
  • D
    96 kg m2/s

Solution

I=2 kg m2, ωo=60 rad s-1
t=5 min=5×60=300 s
∝ =0-60300=-60300=-15 rad s-2
for 2min (from starting) (2 min = 120 sec)
ω=ω0+∝t
=60-15×120=60-24
ω=36 rad s-1 and  L=Iω=2×36=72 kg m2 s-1

Hence, the correct answer is option: 'C'.

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