For occurrence of free torsional vibration which of the condition is necessary?

For occurrence of free torsional vibration in a three rotor system which of the condition is necessary?

A

Rotors moving in same direction

B

Rotors having same frequency

C

Rotors having different frequency

D

Rotors rotate in the same sense

Statement: Resonance is a special case of forced vibration in which the nature and frequency of vibration of the body are the same as the impressed frequency and the amplitude of forced vibration, is maximum. Reason: The amplitude of forced vibrations of a body increases with an increase in the frequency of the externally impressed periodic force.

A

Both statement and reason are true and the reason is the correct explanation of the statement

B

Both statement and reason are true but the reason is not the correct explanation of the statement

C

Statement is true, but the reason is false

D

Statement and reason are false

A machine mounted on a single coil spring has a period of free vibration of $${{\text{t}}_{\text{p}}}$$ . If the spring is cut into four equal parts and placed in parallel and the machine is mounted on them, then the period of free vibration of the new system will become

A

$$\frac{{{{\text{t}}_{\text{p}}}}}{{16}}$$

B

$$\frac{{{{\text{t}}_{\text{p}}}}}{4}$$

C

$$4{{\text{t}}_{\text{p}}}$$

D

$$16{{\text{t}}_{\text{p}}}$$

The natural frequency of free torsional vibrations of a shaft is equal to (where q = Torsional stiffness of the shaft and $$I$$ = Mass moment of inertia of the disc attached at the end of a shaft)

A

$$2\pi \sqrt {\frac{{\text{q}}}{I}} $$

B

$$2\pi \sqrt {{\text{q}}I} $$

C

$$\frac{1}{{2\pi }}\sqrt {\frac{{\text{q}}}{I}} $$

D

$$\frac{1}{{2\pi }}$$

In which of the following condition torsional vibration will not take place, considering 3 rotors A, B and C. A is rotating in clockwise direction.

A

B in clockwise C in anticlockwise

B

C in clockwise B in anticlockwise

C

B and C in clockwise

D

B and C in anticlockwise

For the free torsional vibration of a geared system which of the following statement is true?

A

Backlash in geared system

B

High inertia of shaft

C

Gearing teeth always in contact

D

High inertia of gear

If radius of gyration increases then the torsional free vibration increases.

A

True

B

False

In a three rotor system, free torsional vibration cannot occur if there is only one node.

A

True

B

False

A single cylinder oil engine works with a three rotor system, the shaft length is 2.5m and 70mm in diameter, the middle rotor is at a distance 1.5m from one end. Calculate the free torsional vibration frequency for a single node system in Hz if the mass moment of inertia of rotors in Kg-m2 are: 0.15, 0.3 and 0.09. C=84 kN/mm2

A

171

B

181

C

191

D

201

A single cylinder oil engine works with a three rotor system, the shaft length is 2.5m and 70mm in diameter, the middle rotor is at a distance 1.5m from one end. Calculate the free torsional vibration frequency for a two node system in Hz if the mass moment of inertia of rotors in Kg-m2 are: 0.15, 0.3 and 0.09. C=84 kN/mm2

A

257

B

281

C

197

D

277

For occurrence of free torsional vibration which of the condition is necessary?

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