Question

Calculate the moment of inertia of the disc having a mass of 54 kg and diameter of 91 cm.

(a) 5.512 kgm^2

(b) 5.589 kgm^2

(c) 5.487 kgm^2

(d) 5.018 kgm^2

I have been asked this question in an online quiz.

My query is from DC Motors in section Characteristics of DC & AC Motors of Electric Drives

Answer 1

Correct option is (b) 5.589 kgm^2

The explanation: The moment of inertia of the disc can be calculated using the formula I=mr^2×.5. The mass of the disc and diameter is given. I=(54)×.5×(.455)^2=5.589 kgm^2. It depends upon the orientation of the rotational axis.