Dynamics of Machinery (3151911) MCQs

MCQs of Balancing of Rotating Masses

Showing 1 to 10 out of 16 Questions
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1.

The balancing of rotating and reciprocating parts of an engine is necessary when it runs at

(a)

slow speed 
(b)

medium speed 
(c)

high speed 
(d)

none of the mentioned
Answer:

Option (c)

2.

The static balancing is satisfactory for low-speed rotors but with increasing speeds, dynamic balancing becomes necessary. This is because the

(a)

unbalanced couples are caused only at higher speeds
(b)

unbalanced forces are not dangerous at higher speeds
(c)

effects of unbalances are proportional to the square of the speed
(d)

effects of unbalances are directly proportional to the speed
Answer:

Option (c)

3.

A system in dynamic balance implies that

(a)

the system is critically damped
(b)

there is no critical speed in the system
(c)

the system is also statically balanced
(d)

there will absolutely no wear of bearings
Answer:

Option (c)

4.

A disturbing mass m1 attached to a rotating shaft may be balanced by a single mass m2 attached in the same plane of rotation as that of m1 such that

(a)

m1.r2 = m2.r1 
(b)

m1.r1 = m2.r2 
(c)

m1. m2 = r1.r2
Answer:

Option (b)

5.

For dynamic balancing of a shaft,

(a)

the resultant force must be zero
(b)

the resultant couple must be zero
(c)

both the resultant force and couple must be zero
Answer:

Option (c)

6.

In order to have a complete balance of the several revolving masses in different planes

(a)

the resultant force must be zero
(b)

the resultant couple must be zero
(c)

both the resultant force and couple must be zero
Answer:

Option (c)

7.

Often an unbalance of forces is produced in rotary or reciprocating machinery due to the ______.

(a)

centripetal forces
(b)

centrifugal forces
(c)

friction forces
(d)

inertia forces
Answer:

Option (d)

8.

Which of the following is true for centrifugal force causing unbalance?

(a)

Direction changes with rotation
(b)

Magnitude changes with rotation
(c)

Direction and magnitude both change with rotation
(d)

Direction and magnitude both remain unchanged with rotation
Answer:

Option (a)

9.

In a revolving rotor, the centrifugal force remains balanced as long as the center of the mass of the rotor lies ___________.

(a)

below the axis of the shaft
(b)

on the axis of the shaft
(c)

above the axis of the shaft
(d)

away from the axis of the shaft
Answer:

Option (b)

10.

What is the effect of a rotating mass of a shaft on a system?

(a)

Bend the shaft
(b)

Twist the shaft
(c)

Extend the shaft
(d)

Compress the shaft
Answer:

Option (a)

Showing 1 to 10 out of 16 Questions
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