Mechanics of Textile Machinery (MCQ : MODULE 13- Balancing of Machines )

Question 1: Vibration measurements at bearing supports show unequal amplitude & 120 ° phase difference. The unbalance type is

Static
Pure quasi-static
Pure-couple
Dynamic

Question 2: Which one of the following statements is correct?

In static unbalance, the heavy spot and centre of gravity of rotor are in the same plane
In a multi plane rotor, the unit of heavy spot is mass times the angular speed of rotor
The vibration on bearing is severely affected by the mass of heavy spot than the rotor speed
The unit of unbalance is g-m-s -2.

Question 3: Knife edge method of static balance is very effective for

Multi plane rotor
Heavy rotor operating at high speeds
Light weight single plane rotor operating at low speed
Light weight rotor operating at very high speeds

Question 4: When a unbalanced pulley is mounted on previously balanced motor, then the unbalance will be

Pure couple
Quasi-static
Static
Dynamic

Question 5: Static unbalance is characterized by

Vibrations measured on left and right bearings are of same magnitude and are in phase
Vibrations measured on left and right bearings are of different magnitude and are in phase
Vibrations measured on left and right bearings are of same magnitude and are out of phase by 180°
Vibrations measured on left and right bearings are of different magnitude and the phase difference is greater than 0 ° and less than 180°

Question 6: Pure couple unbalance is characterized by

Vibrations measured on left and right bearings are of same magnitude and are in phase
Vibrations measured on left and right bearings are of different magnitude and are in phase
Vibrations measured on left and right bearings are of same magnitude and are out of phase by 180°
Vibrations measured on left and right bearings are of different magnitude and the phase difference is greater than 0° and less than 180°

Question 7: Dynamic unbalance is characterized by

Vibrations measured on left and right bearings are of same magnitude and are in phase
Vibrations measured on left and right bearings are of different magnitude and are in phase
Vibrations measured on left and right bearings are of same magnitude and are out of phase by 180°
Vibrations measured on left and right bearings are of different magnitude and the phase difference is greater than 0° and less than 180°

Question 8: Which of the following statements are false?

A cam may be perfectly balanced
Trial weights are used for calibrating vibration measuring instruments
Axial run out of a disk create static unbalance
A perfectly round disk may be have unbalance

Question 9: Plane transposition is useful to

Reduce the number of correction weights
Calculate the correction weights to be placed at convenient location of rotor
Reduce the magnitude of correction weights
None of the above

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