Question

If the mass moment of inertia is increased to four times, then what will be the effect on free torsional vibrations of a single motor system?

(a) Increases 4 times

(b) Increases 2 times

(c) Decreases 4 times

(d) Decreases 2 times

This question was posed to me by my school principal while I was bunking the class.

My doubt is from Free Torsional Vibrations of a Single Rotor System in section Torsional Vibrations of Machine Dynamics

Answer 1

The correct choice is (d) Decreases 2 times

For explanation: Since the free torsional vibrations of a single motor system depend on the inverse of square root of the mass moment of inertia of the system, increasing 4 times will lead to decrease in two times the initial vibration.