Question

For a two rotor system, the mass moment of inertia of one shaft(A) is twice the other(B), then what is the relation between the length of the shafts.

(a) 2L(A) = L(B)

(b) L(A) = 2L(B)

(c) L(A) = L(B)

(d) 2L(A) = 3L(B)

I had been asked this question during an interview for a job.

This intriguing question comes from Free Torsional Vibrations of a Two Rotor System topic in division Torsional Vibrations of Machine Dynamics

Answer 1

Correct choice is (a) 2L(A) = L(B)

The best I can explain: For a two rotor system, we have L(A)I(A) = L(B)I(B)

Now I(A)=2I(B)

Therefore, 2L(A) = L(B).