Physics - Rotation Question with Solution | TestHub

PhysicsRotationAngular momentumMedium2 minPYQ_2017
PhysicsMediumsingle choice

A disc of the moment of inertiaI1is rotating in a horizontal plane about an axis passing through a centre and perpendicular to its plane with constant angular speedω1Another disc of the moment of inertiaI2having zero angular speed is placed coaxially on a rotating disc. Now both the disc are rotating with the constant angular speedω2. The energy lost by the initial rotating disc is

Options:

Answer:
D
Solution:

I1ω1=I1+I2ω2
ω2ω1=I1I1+I2
E1-E2
=12I1ω12-12(I1+I2)ω22
=12ω12I1-I1+I2ω22ω12 
=12ω12I1-I1+I2I12I1+I22 
=12ω12I12+I1I2-I12I1+I2=12I1I2I1+I2ω12  

Stream:MHT_CETSubject:PhysicsTopic:RotationSubtopic:Angular momentum
⏱ 2mℹ️ Source: PYQ_2017

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