# Keeping the mass moment of inertia of left end and the right end shafts in a three rotor system same, if the length of one shaft is doubled what should be the effect on the length of other shaft?

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Keeping the mass moment of inertia of left end and the right end shafts in a three rotor system same, if the length of one shaft is doubled what should be the effect on the length of other shaft?

(a) Doubled

(b) Halved

(c) Constant

(d) Increased to 4 times

This question was posed to me during an internship interview.

This question is from Free Torsional Vibrations of a Three Rotor System in section Torsional Vibrations of Machine Dynamics

by (38.6k points)
Correct choice is (a) Doubled

Explanation: The vibration will occur in a two rotor system only if the frequencies of both the rotors are same, hence L(a)I(a) = L(c)I(c). Therefore the relation is directly proportional.

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