AP EAPCET 25-Aug-2021 Shift 2 Paper

From the perpendicular axis theorem, we have
I2=Ix+Iy
where, I2 is moment of inertia about Z-axis,
Ix is moment of inertia about X-axis
and Iy is moment of inertia about Y-axis. Moment of inertia of a disc, Ix=

1

2

MR2
Now, Ix=Iy, because two perpendicular diameters are equivalent.
So, Idiameter=

1

2

×

1

2

MR2=

MR2

4

⇒

MR2

4

=25 (given)
⇒ M=

100

R2

‌kg
Also every diameter passes through centre of mass.
So, ICOM=

MR2

4

=25‌kg−m2
Using parallel axis theorem,
I=ICOM+Mx2 (where, .x=

R

2

)
=25+M

R2

4

=25+

100

R2

×

R2

4

=50‌kg−m2