Question

Three uniform circular disc, each of mass 0.5 kg and radius 10 cm, are kept in contact with each other in fig. Find the MI of the system when it rotates about the axis AB.

Answer 1

Given:

Mass of the disc = m = 0.5 Kg

Radius of the disc = r = 10 cm = 0.1m

To Find:

MI of the system when it rotates about AB axis

Solution:

Let the moments of inertia be I1, I2 and I3 of the discs D1, D2 and D3.

I1 = I2 = mr²/4 + mr²

= 5/4mr²

MI = I1 + I2 + I3

= 2 × 5mr²/4 + mr²/4

= 11mr²/4

= 11 × 0.5 × 0.1 × 0.1 /4

= 1.375 × 10²

Answer: The MI is  1.375 × 10²Kgm²