Question

the moment if inertia of a disc about its diameter is 2 units its moment of inertia about axis through a point on its rim and in the plane of the disc is

Answer 1

 The Moment of Inertia about it's diameter is 2 units. It's MI about axis through a point on it's rim and in the plane of the disc
a) 4units b)6units c)8units d) 10 units.
Two spheres each of mass M and radius R/2 are connected with a massless rod of length 2R. What will be the moment of Inertia of the system about an axis passing through the centre of the one of the spheres and perpendicuar to the rod.
a)21/5 MR2 b) 2/5MR2 c)5/2MR2 d)5/21MR2

Answer 2

⛦Hᴇʀᴇ Is Yoᴜʀ Aɴsᴡᴇʀ⚑
▬▬▬▬▬▬▬▬▬▬▬▬☟

▶Let ‘r’ be the radius of the disc.

♦ Given,

➧ moment of inertia of the disc about PQ, IPQ
➾ 2 units

➧ Moment of inertia of the disc about AB, IAB
➾ ½ Mr²


➧ We need the MI of the disc about RS or IRS.

♦ Now

➧ From theorem of perpendicular axes,

IAB = 2IPQ

➾ ½ Mr² = 2

➾ Mr² = 4

➧ Now, by theorem of parallel axes
IRS

➾ IPQ + Mr²
➾ 2 + 4
➾ 6 units ...✔

_________
Thanks...✊