Chapter:

30+ Balancing Solved MCQs

in Dynamics of Machinery

These multiple-choice questions (MCQs) are designed to enhance your knowledge and understanding in the following areas: Mechanical Engineering .

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1.	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» A. Direction changes with rotation

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2.	If the unbalanced system is not set right then.
A.	Static forces develop
B.	Dynamic forces develop
C.	Tangential forces develop
D.	Radial forces develop
Answer» A. Static forces develop

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3.	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» A. Bend the shaft

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4.	In a revolving rotor, the centrifugal force remains balanced as long as the centre of the mass of the rotor lies ___________
A.	Below the axis of shaft
B.	On the axis of the shaft
C.	Above the axis of shaft
D.	Away from the axis of shaft
Answer» B. On the axis of the shaft

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5.	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» D. Inertia forces

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6.	The mass used to balance the mass defect is known as ______
A.	Balancing mass
B.	Defect mass
C.	Replacement mass
D.	Fixing mass
Answer» A. Balancing mass

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7.	In balancing of single-cylinder engine, the rotating unbalance is ____________
A.	completely made zero and so also the reciprocating unbalance
B.	completely made zero and the reciprocating unbalance is partially reduced
C.	partially reduced and the reciprocating unbalance is completely made zero
D.	partially reduced and so also the reciprocating unbalance
Answer» B. completely made zero and the reciprocating unbalance is partially reduced

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8.	Let the disturbing mass be 100 kg and the radius of rotation be 10 cm and the rotation speed be 50 rad/s, then calculate the centrifugal force in kN.
A.	50
B.	25
C.	50000
D.	25000
Answer» B. 25

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9.	Which of the following statement is correct?
A.	In any engine, 100% of the reciprocating masses can be balanced dynamically
B.	In the case of balancing of multicylinder engine, the value of secondary force is higher than the value of the primary force
C.	In the case of balancing of multimass rotating systems, dynamic balancing can be directly started without static balancing done to the system
D.	none of the mentioned
Answer» C. In the case of balancing of multimass rotating systems, dynamic balancing can be directly started without static balancing done to the system

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10.	If all the masses are in one plane, then what is the maximum no. of masses which can be placed in the same plane?
A.	3
B.	4
C.	6
D.	No limitation
Answer» D. No limitation

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11.	Which of the following statements is correct about the balancing of a mechanical system?
A.	If it is under static balance, then there will be dynamic balance also
B.	If it is under dynamic balance, then there will be static balance also
C.	Both static as well as dynamic balance have to be achieved separately
D.	None of the mentioned
Answer» C. Both static as well as dynamic balance have to be achieved separately

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12.	In a locomotive, the ratio of the connecting rod length to the crank radius is kept very large in order to
A.	minimize the effect of primary forces
B.	minimize the effect of secondary forces
C.	have perfect balancing
D.	start the locomotive conveniently
Answer» B. minimize the effect of secondary forces

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13.	Secondary forces in reciprocating mass on engine frame are
A.	of same frequency as of primary forces
B.	twice the frequency as of primary forces
C.	four times the frequency as of primary forces
D.	none of the mentioned
Answer» B. twice the frequency as of primary forces

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14.	For a V-twin engine, which of the following means can be used to balance the primary forces?
A.	Revolving balance mass
B.	Rotating balance mass
C.	Reciprocating balance mass
D.	By the means of secondary forces
Answer» A. Revolving balance mass

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15.	The primary unbalanced force is maximum when the angle of inclination of the crank with the line of stroke is
A.	0°
B.	90°
C.	180°
D.	360°
Answer» C. 180°

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16.	From the following data of a 60 degree V-twin engine, determine the minimum value for primary forces in newtons:Reciprocating mass per cylinder = 1.5 Kg Stroke length = 10 cm Length of connecting rod = 25 cm Engine speed = 2500 rpm
A.	7711
B.	4546
C.	2570
D.	8764
Answer» C. 2570

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17.	From the following data of a 60 degree V-twin engine, determine the maximum value for primary forces in newtons:Reciprocating mass per cylinder = 1.5 Kg Stroke length = 10 cm Length of connecting rod = 25 cm Engine speed = 2500 rpm
A.	7711
B.	4546
C.	2570
D.	8764
Answer» A. 7711

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18.	In the given figure, m1=10 Kg, m2=30Kg and m=50 Kg, if r=0.3m, l=1m, find l2 = 0.5m, find r1 in m.
A.	1.5
B.	0.75
C.	3
D.	6
Answer» B. 0.75

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19.	From the given data, find the balancing mass’s inclination in degrees if r=0.2m required in the same plane.Masses = 200kg, 300kg, 240 kg, 260Kg,
A.	201.48
B.	200.32
C.	210.34
D.	202.88
Answer» A. 201.48

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20.	Which of the following statements are associated with complete dynamic balancing of rotating systems? 1. Resultant couple due to all inertia forces is zero. 2. Support reactions due to forces are zero but not due to couples . 3. The system is automatically statically balanced. 4. Centre of masses of the system lies on the axis of rotation.
A.	1, 2, 3 and 4
B.	1, 2, and 3 only
C.	2, 3 and 4 only
D.	1, 3 and 4 only
Answer» D. 1, 3 and 4 only

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21.	A V-twin engine has the cylinder axes at 90 degrees and the connecting rods operate a common crank. The reciprocating mass per cylinder is 11.5 kg and the crank radius is 7.5 cm. The length of the connecting rod is 0.3 m. If the engine is rotating at the speed is 500 r.p.m. What is the value of maximum resultant secondary force in Newtons?
A.	736
B.	836
C.	936
D.	636
Answer» B. 836

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22.	Let the centrifugal force in kN be 25 and the radius of rotation be 20 cm and the rotation speed be 50 rad/s, then calculate the mass defect in Kg.
A.	50
B.	25
C.	50000
D.	25000
Answer» A. 50

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23.	In a multicylinder inline engine, each imaginary secondary crank with a mass attached to the crankpin is inclined to the line of stroke at which angle?
A.	Twice the angle of crank
B.	Half the angle of crank
C.	Thrice the angle of crank
D.	Four times the angle of crank
Answer» A. Twice the angle of crank

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24.	In order to achieve stability, the sum of secondary forces and secondary couples must be ------- and their respective polygons must be …......
A.	Zero, Closed
B.	one, Open
C.	Zero, open
D.	one, closed
Answer» A. Zero, Closed

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25.	For the secondary balancing of the engine, which of the condition is necessary?
A.	Secondary force polygon must be close
B.	Secondary force polygon must be open
C.	Primary force polygon must be close
D.	Primary force polygon must be open
Answer» A. Secondary force polygon must be close

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26.	The numerical values of the secondary forces and secondary couples couples may be obtained by considering the ___________
A.	Revolving mass
B.	Reciprocating mass
C.	Translating mass
D.	Rotating mass
Answer» A. Revolving mass

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27.	Which of the following is the correct expression for secondary force?
A.	m𝜔^2r.cos2θ/n
B.	m 𝜔^2r.sin2θ/n
C.	m𝜔^2r.tan2θ/n
D.	m𝜔^2r.cosθ/n
Answer» A. m𝜔^2r.cos2θ/n

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28.	A V-twin engine has the cylinder axes at 90 degrees and the connecting rods operate a common crank. The reciprocating mass per cylinder is 23 kg and the crank radius is 7.5 cm. The length of the connecting rod is 0.3 m. If the engine is rotating at the speed is 500 r.p.m. What is the value of maximum resultant secondary force in Newtons?
A.	7172
B.	1672
C.	1122
D.	1272
Answer» B. 1672

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29.	A V-twin engine has the cylinder axes at 90 degrees and the connecting rods operate a common crank. The reciprocating mass per cylinder is 34.5 kg and the crank radius is 7.5 cm. The length of the connecting rod is 0.3 m. If the engine is rotating at the speed is 500 r.p.m. What is the value of maximum resultant secondary force in kN?
A.	2.238
B.	2.508
C.	2.754
D.	2.908
Answer» B. 2.508

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30.	From the given data, find the balancing mass in Kg if r=0.2m required in the same plane.Masses = 200kg, 300kg, 240 kg, 260Kg, corresponding radii = 0.2m, 0.15m, 0.25m and 0.3m.Angles between consecutive masses = 45, 75 and 135 degrees.
A.	116
B.	58
C.	232
D.	140
Answer» A. 116

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31.	Let the disturbing mass be 200 kg and the radius of rotation be 20 cm and the rotation speed be 50 rad/s, then calculate the centripetal force in kN.
A.	-50
B.	-25
C.	-100
D.	-2500
Answer» C. -100

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32.	From the given data, calculate the unbalanced centrifugal force in N s2 Distance from shaft = 0.2 m Mass = 100 kg Rotating speed = 1000 rpm.
A.	20
B.	2×10^7
C.	200
D.	20000
Answer» C. 200

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33.	Let the disturbing mass be 50 Kg, with radius of rotation = 0.1m, if one of the balancing mass is 30 Kg at a radius of rotation 0.1m then find the other balancing mass situated at a distance of 0.2m.
A.	80
B.	40
C.	20
D.	10
Answer» D. 10

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34.	In the given figure, m1=20 Kg, m2=30Kg and m=50 Kg, if r1=0.2m and r=0.3m, l=1m, find l2.
A.	0.26m
B.	0.52m
C.	1.04m
D.	13m
Answer» A. 0.26m

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30+ Balancing Solved MCQs

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

If the unbalanced system is not set right then.

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

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

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

The mass used to balance the mass defect is known as ______

In balancing of single-cylinder engine, the rotating unbalance is ____________

Let the disturbing mass be 100 kg and the radius of rotation be 10 cm and the rotation speed be 50 rad/s, then calculate the centrifugal force in kN.

Which of the following statement is correct?

If all the masses are in one plane, then what is the maximum no. of masses which can be placed in the same plane?

Which of the following statements is correct about the balancing of a mechanical system?

In a locomotive, the ratio of the connecting rod length to the crank radius is kept very large in order to

Secondary forces in reciprocating mass on engine frame are

For a V-twin engine, which of the following means can be used to balance the primary forces?

The primary unbalanced force is maximum when the angle of inclination of the crank with the line of stroke is

From the following data of a 60 degree V-twin engine, determine the minimum value for primary forces in newtons:Reciprocating mass per cylinder = 1.5 Kg Stroke length = 10 cm Length of connecting rod = 25 cm Engine speed = 2500 rpm

From the following data of a 60 degree V-twin engine, determine the maximum value for primary forces in newtons:Reciprocating mass per cylinder = 1.5 Kg Stroke length = 10 cm Length of connecting rod = 25 cm Engine speed = 2500 rpm

In the given figure, m1=10 Kg, m2=30Kg and m=50 Kg, if r=0.3m, l=1m, find l2 = 0.5m, find r1 in m.

From the given data, find the balancing mass’s inclination in degrees if r=0.2m required in the same plane.Masses = 200kg, 300kg, 240 kg, 260Kg,

Let the centrifugal force in kN be 25 and the radius of rotation be 20 cm and the rotation speed be 50 rad/s, then calculate the mass defect in Kg.

In a multicylinder inline engine, each imaginary secondary crank with a mass attached to the crankpin is inclined to the line of stroke at which angle?

In order to achieve stability, the sum of secondary forces and secondary couples must be ------- and their respective polygons must be …......

For the secondary balancing of the engine, which of the condition is necessary?

The numerical values of the secondary forces and secondary couples couples may be obtained by considering the ___________

Which of the following is the correct expression for secondary force?

From the given data, find the balancing mass in Kg if r=0.2m required in the same plane.Masses = 200kg, 300kg, 240 kg, 260Kg, corresponding radii = 0.2m, 0.15m, 0.25m and 0.3m.Angles between consecutive masses = 45, 75 and 135 degrees.

Let the disturbing mass be 200 kg and the radius of rotation be 20 cm and the rotation speed be 50 rad/s, then calculate the centripetal force in kN.

From the given data, calculate the unbalanced centrifugal force in N s2 Distance from shaft = 0.2 m Mass = 100 kg Rotating speed = 1000 rpm.

Let the disturbing mass be 50 Kg, with radius of rotation = 0.1m, if one of the balancing mass is 30 Kg at a radius of rotation 0.1m then find the other balancing mass situated at a distance of 0.2m.

In the given figure, m1=20 Kg, m2=30Kg and m=50 Kg, if r1=0.2m and r=0.3m, l=1m, find l2.