In a two rotor system, torsional vibration occurs only if the rotors are moving in the same direction.

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

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

Which of the following is/are appropriate care and maintenance of centrifuges? I. Proper balancing of centrifuge tubes. II. Avoid long time exposure of the rotors to alkaline solution and acidic buffers. III. Cleaning centrifuges and rotors with coarse brushes and then wash them with distilled or de-ionized water after every run. IV. For overnight storage, the rotors are left upside down and then positioned in a safe and dry place.

A

I, II, III only

B

II, III and IV only

C

I, II, and IV only

D

II only

Free torsional vibrations will occur in a two rotor system only if both rotors have same frequency.

A

True

B

False

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

Free torsional vibrations will occur in a three rotor system only if all rotors have same frequency.

A

True

B

False

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

A

True

B

False

In a three rotor system, for the middle rotor, if the stiffness of both the length either side of the rotor is increased to two times what will be the effect on total stiffness of the middle rotor?

A

Remains constant

B

Decreases by two times

C

Increases by two times

D

Increases by 4 times

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

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

In a two rotor system, torsional vibration occurs only if the rotors are moving in the same direction.

Related Questions