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Dynamics of Machineries (DM) MCQ with Answer [1-60].

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 Dynamics of Machineries (DM) MCQ with Answer [1-60].


Mechanical engineering last year subject dynamics of machineries or DM mcq question with answer for online exam and interview preperation purpose.


Q.no 1. If the polar moment of inertia is increased to four times, then what will be the effect on free torsional vibrations of a single rotor system?


A : Increases 4 times

B : Increases 2 times

C : Decreases 4 times

D : Decreases 2 times

Answer :-  A

Q.no 2. To measure the displacement what is used


A : Vibrometer

B : accelerometer

C : velometer

D : frequency meter

Answer :- A

Explanation :- To measure the displacement vibrometer are used.

Q.no 3. Balancing of a rigid rotor can be achieved by appropriately placing balancing weights in

A : a single plane

B : two plane

C : three planes

D : four planes

Answer :- B

Explanation :- Balancing of a rigid rotor can be achieved by approprietly placing balancing weights in two planes.

Q.no 4. The main properties of a vibrating system are

A : mass and stiffness

B : mass, stiffness and damper

C : stiffness and damper

D : none of these

Answer :- B

Explanation :- Main properties of vibrating system are Stiffness, Mass and Damper.

Q.no 5. Force required to produce unit displacement is

A : Amplitude

B : Frequency

C : Time period

D : Stiffness

Answer :- D

Explanation :- Force required to produce unit displacement is Stiffness.

Q.no 6. How many differenial equations are written for two degree of freedom system

A : One

B : Two

C : Three

D : Four

Answer :- B

Q.no 7. What is used to measure the velocity component

A : Vibrometer

B : accelerometer

C : velometer

D : frequency meter

Answer :- C

Q.no 8. Noise that is produced by combining sounds of all different frequenices together withi the range of human hearing is called as

A : Sound pressure level

B : White Noise

C : Pure tone

D : Sound intensity

Answer :- B

Q.no 9. When the amplitude of vibration of the main system , while operating at at its original resonant frewuency, becomes zero, then it is called as ---------- absorber.

A : tunned

B : untunned

C : uncontrolled

D : None of the above

Answer :- A

Q.no 10. In which direction does the accelerating force acts?

A : Opposite to the motion

B : Along the motion

C : Perpendicular to motion

D : Variable

Answer :- B

Q.no 11. Measurement of natural frequncy helps

A : to select the material

B : to select the mass

C : to select the operating speed

D : to select the operator

Answer :- C

Q.no 12. Vibrations due to earthquake is an example of

A : Linear vibration

B : Random vibration

C : all of these

D : none of these

Answer :- B

Q.no 13. for static balancing of shaft

A : the dynamic force acting on the shaft is equal to zero

B : the net couple due to the dynamic force acting on the shaft is equal to zero

C : Both (1) and (2)

D : the net couple due to the dynamic force acting on the shaft is not equal to zero

Answer :- C

Q.no 14. 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 & couple must be zero

D : the resultant couple must be equal to one

Answer :- C

Q.no 15. A machine operating at 1800 rpm is vibrating due to rotating unbalance.The frequency of vibration is

A : 18.8 rad/s

B : 188 rad/s

C : 30 rad/s

D : Insufficient data

Answer :- B

Q.no 16. Critical damping coefficient depends on

A : mass of the system

B : stiffness of the spring

C : Both mass of the system and stiffness of the system.

D : none of these

Answer :- C

Q.no 17. In two degrees of freedom system to describe the motion completely we need

A : Two independent coordinates

B : Two dependent coordinates

C : One independent and one dependent coordinator

D : Both dependent coordinators

Answer :- A

Q.no 18. Indoor noise can be caused by ?

A : home appliances

B : honking

C : vehicles

D : construction equipments

Answer :- A

Q.no 19. Sound enclosure is type of noise control at

A : receiver

B : path

C : source

D : structure

Answer :- C

Q.no 20. Oscillation of simple pendulum is an example of

A : forced vibration

B : free vibration

C : none of these

D : all of these

Answer :- B

Q.no 21. The number of natural frequencies in case of cantilever beam is

A : infinite

B : 1

C : 2

D : 3

Answer :- A

Q.no 22. Which of the following is not a controlling parameter in transmissibility curve?

A : Mass region

B : Damping region

C : Stiffness region

D : Motion region

Answer :- D

Q.no 23. When the ration of main mass to absorbeer mass is very small, then absorber becomes ---------

A : highly effective

B : less effective

C : unaffected

D : none of the above

Answer :- B

Q.no 24. Natural frequency of simple spring mass system depends on

A : spring constant

B : mass of the system

C : both spring constant and mass of the system

D : none of these

Answer :- C

Q.no 25. The region in a medium in which sound waves are being propagated from the source of sounds is

A : Sound fields

B : Sound wave

C : Acoustic intensity

D : Overall sound pressure

Answer :- A

Q.no 26. If a system is having three degree of freedom , how many natural frequencies it will have?

A : 1

B : 2

C : 3

D : 4

Answer :- C

Q.no 27. Which of the following relations is true for viscous damping?

A : Force proportional to relative displacement

B : Force proportional to relative velocity

C : Force inversely proportional to relative velocity

D : None of the above

Answer :- B

Q.no 28. In order to balance the reciprocating masses,

A : primary forces and couples must be balanced

B : secondary forces and couples must be balanced

C : both (a) and (b)

D : none of these

Answer :- C

Q.no 29. In steady state forced vibrations, the amplitude of vibrations at resonance is how much to damping coefficient?

A : Equal to

B : Directly proportional to

C : Indirectly proportional to

D : Independent of

Answer :- C

Q.no 30. Materials made from vegetable and mineral fibers, elastomeric foams, glass blankets, fiber boards are example of

A : Membrane sound absorber material

B : Resonators sound absorber material

C : Porous sound absorber material

D : Non-porous panels

Answer :- C

Q.no 31. Which of the following methods can be used to reduce excitation level at the source?

A : Lubrication of joints

B : Balancing inertia forces

C : Both 1. and 2.

D : None of the above

Answer :- C

Q.no 32. Secondary force in reciprocating engine mechanism is caused due to _______

A : S.H.M. of reciprocating parts

B : oscillation of reciprocating parts

C : obliquity of arrangement of reciprocating parts

D : All of the above

Answer :- C

Q.no 33. In a harmonically excited single DOF mass-spring-damper system, the phase of damping force is

A : In phase with the spring force

B : Out of phase with the spring force

C : 90 degree behind the spring force

D : 90degree ahead of the spring force

Answer :- D

Q.no 34. 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

Answer :- B

Q.no 35. Each reed in multireed frequncy meter is of

A : Different height

B : same natural frequncy

C : different natural frequency

D : all of the above

Answer :- C

Q.no 36. At a nodal point in the shaft, the frequency of vibration is

A : Zero

B : Double than at the ends

C : Minimum

D : Maximum

Answer :- A

Q.no 37. A device which converts acoustical energy into electrical energy

A : Sound level meter

B : Sound frequency analyser

C : Recorders

D : Microphone

Answer :- D

Q.no 38. 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

Q.no 39. Far field consist of

A : Near field and Free field

B : Near field and Diffused field

C : Near field and Reverberant field

D : Free field and Reverbant field

Answer :- D

Q.no 40. 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

Q.no 41. For a gearing system, the equivalent system is made consisting of two rotors. How many nodes will this new equivalent system will have?

A : 0

B : 2

C : 1

D : 3

Answer :- A

Q.no 42. Chamber used for testing acoustic energy from sound is

A : Transmission Chamber

B : Reflection Chamber

C : Reverberation Chamber

D : Absorption Chamber

Answer :- C

Q.no 43. Let the disturbing mass be 100 kg and the radius of rotation be 20 cm and the rotation speed be 50 rad/sec then calculate the centrifugal force in kN.

A : 25

B : 50

C : 25000

D : 50000

Answer :- B

Q.no 44. If damping factor is 0.5 and ratio of working frequency to natural frequency is 1.5. Amplitude of system is given by 50 mm find the sine wave of the profile.

A : 5.4 mm

B : 54 mm

C : 5.4 m

D : 54 m

Answer :- B

Q.no 45. The road profile is approximated with a sine wave of 40mm and ratio of working frequency to natural frequency is given by 2.25. Find the amplitude of the system when damping factor is 0.2.

A : 12.93 m

B : 12.93 mm

C : 1.293 m

D : 1.293 mm

Answer :- B

Q.no 46. Pre-amplifier, attenuator, amplifier, filter and rectifier are various elements of

A : Sound level meter

B : Sound frequency analyser

C : Recorders

D : Microphone

Answer :- A

Q.no 47. When there is a reduction in amplitude over every cycle of vibration, then the body is said to have

A : free vibration

B : forced vibration

C : damped vibration

D : None of the above

Answer :- C

Q.no 48. The viscous damper of damping coefficienet is 3000N-s/m and damping factor is given 0.3. Find the critical damping coefficient

A : 10 N-s/m

B : 100 N-s/m

C : 1000 N-s/m

D : 10000 N-s/m

Answer :- D

Q.no 49. As per survey about community noise in urban areas, the percentage of noise contribution is 'maximum' in following source

A : Heavy Industries

B : Construction Activities

C : Entertainment

D : Transportation

Answer :- D

Q.no 50. If the damping factor is unity the system refers to

A : critical damped system

B : Over damped system

C : under damped system

D : all of these

Answer :- A

Q.no 51. If isolation factor is negative, then what is the phase difference between transmitted and disturbing force?

A : 180°

B : 90°

C : 450°

D : 360°

Answer :- A

Q.no 52. If the mass of a body increases 9 times

A : frequency decreases 3 times

B : frequency does not change

C : will be zero

D : frequency decreases 4 times

Answer :- A

Q.no 53. Anechoic chamber is

A : reflective, non-echoing

B : non-reflective, non-echoing

C : non-reflective, echoing

D : reflective, echoing

Answer :- B

Q.no 54. Which of the following is the example of two degree of freedom system

A : Simple pendulum

B : Semi-definate system

C : Cantilever beam

D : simply supported beam

Answer :- B

Q.no 55. In vibration isolation system, if ω/ωn > 1, then the phase difference between the transmitted force and the disturbing force is -------

A : 0°

B : 90°

C : 180°

D : 270°

Answer :- C

Q.no 56. A vehicle of mass 490kg and total spring constant of suspension system is 58800 N/m. The profile of the road may be approximated to a sine wave of amplitude 40 mm and wavelength of 4 m. Find the critical speed of the vehicle

A : 2.51 km/hr

B : 25.1 km/hr

C : 251 km/hr

D : 0.251m/hr

Answer :- B

Q.no 57. When the primary direct crank of a reciprocating engine makes an angle θ with the line of stroke, then the secondary direct crank will make an angle of_______with the line of stroke.

A : θ /2

B :  θ

C : 4θ

D : 2θ

Answer :- D

Q.no 58. The amount of cracks and openings in acoustic enclosure should be ?

A : Minimum

B : Maximum

C : Substantial

D : Adequate

Answer :- A

Q.no 59. A vertical spring mass system has a mass of 0.5 kg and an initial deflection of 0.2 cm find the value of natural frequency

A : 11.14 Hz

B : 10.23 Hz

C : 8.97 Hz

D : 7.96 Hz

Answer :- A

Q.no 60. Pass-by noise measurements can actually be simulated indoor using a suitable

A : Anechoic chamber

B : Partial-anechoic chamber

C : Hemi-anechoic chamber

D : Reverberation Chamber


Answer :- C



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