Question

a metalic masss of 1 kg has moment of inertia 1 kg n^2 when rotating about one of its diameters. it is molten and remoulded into a thin uniform disc of the same radius . how much will its moment of inertia be, when roatated about its own axis.


please help me by solving on page

Answer 1

Explanation:

Mass of ring and disc is M=1mkg

Moment of inertia of ring at diameter (Ir)d=1kgm

2

Rr=Rd

What we have to find out:-

Moment of inertia of disc about own axis =Id= ?

Using theorem of perpendicular axes, for a ring M.I about its any diameter, which is given by,

(Ir)c=2(Ir)d

=2×1

MRr

2

=2kgm

2

Rr

2

=Rd

2

=2 meter

Hence,

Moment of inertia of disc about own axis is given by,

Id=

2

1

MRd

2

=

2

1

×1×2

Id=1kgm

2

Hope its help..