JEE Main Physics Class 11 System of Particles and Rotational Motion Part 1 Questions

Moment of inertia of circular disc I1=

1

2

MR2
When two small sphere are attached on the edge of the disc, the moment of inertia becomes
I2=

1

2

MR2+2mR2
When two small spheres of mass m are attached gently, the external torque, about the axis of rotation, is zero and therefore the angular momentum about the axis of rotation is constant.
∴I1ω1=I2ω2⇒ω2=

I1

I2

ω1
∴ω2=

1 2 MR2

1 2 MR2+2mR2

×ω1 =

M

M+4m

ω1