Dynamics of Machinery Test - Set - 2

1)   The noise level generated by domestic air conditioner ranges between _________

a. 38 dB to 70 dB
b. 35 dB to 52 dB
c. 62 dB to 88 dB
d. 50 dB to 60 dB
Answer  Explanation  Related Ques

ANSWER: 50 dB to 60 dB

Explanation:
No explanation is available for this question!


2)   Which of the following construction equipments have highest noise level?

a. Compressors
b. Generators
c. Pneumatic wrenches
d. Pumps
Answer  Explanation  Related Ques

ANSWER: Pneumatic wrenches

Explanation:
No explanation is available for this question!


3)   Which type of earplugs contain silicon rubber and a fixing agent?

a. Semi insert protectors
b. Custom moulded earplugs
c. Pre-fabricated earplugs
d. Canal caps
Answer  Explanation  Related Ques

ANSWER: Custom moulded earplugs

Explanation:
No explanation is available for this question!


4)   Which of the following absorptive treatment can be used to cover the interior of a box to prevent the reverberant sound?

a. Open cell foam
b. Glass fiber mat
c. Both a. and b.
d. None of the above
Answer  Explanation  Related Ques

ANSWER: Both a. and b.

Explanation:
No explanation is available for this question!


5)   What is meant by Reverberant chamber?

a. Chambers having walls, ceiling and flooring acoustically reflected
b. Chambers having walls, ceiling and flooring covered by sound absorbing materials
c. Chambers having walls and ceiling made of different absorbing material
d. None of the above
Answer  Explanation  Related Ques

ANSWER: Chambers having walls, ceiling and flooring acoustically reflected

Explanation:
No explanation is available for this question!


6)   Determine velocity of sound in air at 50o.

(For air, γ = 1.4)


a. 1002.5 m/s
b. 360.45 m/s
c. 350 m/s
d. None of the above
Answer  Explanation  Related Ques

ANSWER: 360.45 m/s

Explanation:
No explanation is available for this question!


7)   Sound wave has a frequency of 8 kHz at 22o C. Determine its wavelength.

a. 0.043 m
b. 0.039 m
c. 0.125 m
d. 0.0125 m
Answer  Explanation  Related Ques

ANSWER: 0.043 m

Explanation:
No explanation is available for this question!


8)   What is the range of audible sound pressure to which a human ear can be subjected to?

a. 10-5 N/m2 to 10-12 N/m2
b. 10-12 W/m2 to 10 W/m2
c. 2 x 10-5 N/m2 to 200 N/m2
d. 2 x 10-5 N/m2 to 300 N/m2
Answer  Explanation  Related Ques

ANSWER: 2 x 10-5 N/m2 to 200 N/m2

Explanation:
No explanation is available for this question!


9)   Which of the following is the reference pressure often referred to as threshold of hearing at 1000 Hz?

a. 5 x 10-5 N/m2
b. 3 x 10-5 N/m2
c. 2 x 10-5 N/m2
d. None of the above
Answer  Explanation  Related Ques

ANSWER: 2 x 10-5 N/m2

Explanation:
No explanation is available for this question!


10)   What will be the sound power level, if a machine generates 20 W power?

a. 124 dB
b. 133 dB
c. 150 dB
d. 200 dB
Answer  Explanation  Related Ques

ANSWER: 133 dB

Explanation:
No explanation is available for this question!


11)   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  Explanation  Related Ques

ANSWER: obliquity of arrangement of reciprocating parts

Explanation:
No explanation is available for this question!


12)   At which angle primary unbalanced force in reciprocating engine mechanism is maximum?

a. 0o
b. 90o
c. 360o
d. All of the above
Answer  Explanation  Related Ques

ANSWER: 0o

Explanation:
No explanation is available for this question!


13)   Which of the following conditions should be satisfied for complete balancing of multi-cylinder inline engines?

a. Primary couples should be balanced
b. Secondary couples should be balanced
c. Both a. and b.
d. None of the above
Answer  Explanation  Related Ques

ANSWER: Both a. and b.

Explanation:
No explanation is available for this question!


14)   Which of the following statements is/are true primary/secondary couple?

1. Secondary couple does not act on V engine
2. Primary couple acts on V engine
3. Secondary couple acts on reciprocating masses of multi-cylinder inline engines
4. Primary couple acts on reciprocating masses of multi-cylinder inline engines


a. 1 and 2
b. 2, 3 and 4
c. 1, 3 and 4
d. All of the above
Answer  Explanation  Related Ques

ANSWER: 1, 3 and 4

Explanation:
No explanation is available for this question!


15)   The unbalanced primary couple caused due to reciprocating mass of each cylinder is given as

a. mrlω2 cos θ
b. mrlω (cos θ / n)
c. mrlω2 cos 2θ
d. mrω2 cos 2θ
Answer  Explanation  Related Ques

ANSWER: mrlω2 cos θ

Explanation:
No explanation is available for this question!


16)   Which of the following relations is true when springs are connected parallelly?
where K = spring stiffness


a. Ke = K1 + K2
b. (1 / Ke) = (1/K1) + (1/ K2)
c. Ke = (1/K1) + (1/ K2)
d. None of the above
Answer  Explanation  Related Ques

ANSWER: Ke = K1 + K2

Explanation:
No explanation is available for this question!


17)   During transverse vibrations, shaft is subjected to which type of stresses?

a. Tensile stresses
b. Torsional shear stress
c. Bending stresses
d. All of the above
Answer  Explanation  Related Ques

ANSWER: Bending stresses

Explanation:
No explanation is available for this question!


18)   Which type of vibrations are also known as transient vibrations?

a. Undamped vibrations
b. Damped vibrations
c. Torsional vibrations
d. Transverse vibrations
Answer  Explanation  Related Ques

ANSWER: Damped vibrations

Explanation:
No explanation is available for this question!


19)   Two springs have spring stiffness of 1500 N/m and 2000 N/m respectively. If they are connected in series, what is the spring stiffness if they are replaced by an equivalent system.3500 N/m

a. 3500 N/m
b. 1166 N/m
c. 857.63 N/m
d. None of the above
Answer  Explanation  Related Ques

ANSWER: 857.63 N/m

Explanation:
No explanation is available for this question!


20)   Calculate equivalent stiffness of the spring for the system shown below, which has spring stiffness of 3000 N/m

Spring-Stiffness.png
a. 1000 N/m
b. 2250 N/m
c. 2000 N/m
d. None of the above
Answer  Explanation  Related Ques

ANSWER: 2250 N/m

Explanation:
No explanation is available for this question!


21)   Eddy current damping is an example of _____

a. Coulomb damping
b. Hysteresis damping
c. Viscous damping
d. Dry friction damping
Answer  Explanation  Related Ques

ANSWER: Viscous damping

Explanation:
No explanation is available for this question!


22)   Which of the following relations is true for viscous damping?

a. Force α relative displacement
b. Force α relative velocity
c. Force α (1 / relative velocity)
d. None of the above
Answer  Explanation  Related Ques

ANSWER: Force α relative velocity

Explanation:
No explanation is available for this question!


23)   What is meant by critical damping coefficient?

a. Frequency of damped free vibrations is less than zero
b. The motion is aperiodic in nature
c. Both a. and b.
d. None of the above
Answer  Explanation  Related Ques

ANSWER: The motion is aperiodic in nature

Explanation:
No explanation is available for this question!


24)   Which of the following statements is/are true for coulomb damping?

1. Coulomb damping occurs due to friction between two lubricated surfaces
2. Damping force is opposite to the direction of motion of vibrating body
3. For smooth surfaces, coefficient of friction depends upon velocity
4. Damping force depends upon the rubbing velocity between two rubbing surfaces


a. Only statement 1
b. Statement 2, 3 and statement 4
c. Only statement 2
d. All the above statements are true
Answer  Explanation  Related Ques

ANSWER: Only statement 2

Explanation:
No explanation is available for this question!


25)   According to D' Alembert's principle, m (d2x/ dt2) + c (dx/dt) + Kx =0 is the differential equation for damped free vibrations having single degree of freedom. What will be the solution to this differential equation if the system is critically damped?

a. x = (A + Bt) e– ωt
b. x = X e– ξωt (sin ωdt + Φ)
c. x = (A – Bt) e– ωt
d. x = X e– ξωt (cos ωdt + Φ)
Answer  Explanation  Related Ques

ANSWER: x = (A + Bt) e– ωt

Explanation:
No explanation is available for this question!


26)   In damped free vibrations, which parameters indicate vibrations?

a. Natural frequency
b. Rate of decay of amplitude
c. Both a. and b.
d. None of the above
Answer  Explanation  Related Ques

ANSWER: Both a. and b.

Explanation:
No explanation is available for this question!


27)   Calculate natural frequency of damped vibration, if damping factor is 0.52 and natural frequency of the system is 30 rad/sec which consists of machine supported on springs and dashpots.

a. 25.62 rad/sec
b. 20.78 rad/sec
c. 14.4 rad/sec
d. 15.33 rad/sec
Answer  Explanation  Related Ques

ANSWER: 25.62 rad/sec

Explanation:
No explanation is available for this question!


28)   At which frequency ratio, phase angle increases as damping factor increases?

a. When frequency ratio is less than unity
b. When frequency ratio is more than unity
c. When frequency ratio is zero
d. All of the above
Answer  Explanation  Related Ques

ANSWER: When frequency ratio is less than unity

Explanation:
No explanation is available for this question!


29)   When frequency ratio (ω/ωn) is greater than unity, phase angle decreases as ______

a. damping factor increases
b. damping factor decreases
c. both a. and b.
d. none of the above
Answer  Explanation  Related Ques

ANSWER: damping factor increases

Explanation:
No explanation is available for this question!


30)   What is the effect of damping on phase angle at resonance frequency?

a. Phase angle increases as damping increases
b. Damping has no effect on phase angle
c. Phase angle increases as damping decreases
d. None of the above
Answer  Explanation  Related Ques

ANSWER: Damping has no effect on phase angle

Explanation:
No explanation is available for this question!


31)   Calculate damped natural frequency, if a spring mass damper system is subjected to periodic disturbing force of 30 N. Damping coefficient is equal to 0.76 times of critical damping coefficient and undamped natural frequency is 5 rad/sec

a. 3.99 rad/sec
b. 2.13 rad/sec
c. 4.12 rad/sec
d. 3.24 rad/sec
Answer  Explanation  Related Ques

ANSWER: 3.24 rad/sec

Explanation:
No explanation is available for this question!


32)   Calculate critical speed of a vehicle which moves on a road having sinusoidal profile of wavelength 2.5 m. The mass of the vehicle is 300 kg and natural frequency of its spring suspension system is 8 rad/sec

a. 4.15 m/sec
b. 3.18 m/sec
c. 2.36 m/sec
d. None of the above
Answer  Explanation  Related Ques

ANSWER: 3.18 m/sec

Explanation:
No explanation is available for this question!


33)   What is meant by node point?

a. The point at which amplitude of vibration is maximum
b. The point at which amplitude of vibration is minimum
c. The point at which amplitude of vibration is zero
d. None of the above
Answer  Explanation  Related Ques

ANSWER: The point at which amplitude of vibration is zero

Explanation:
No explanation is available for this question!


34)   What is meant by coupled differential equation?

a. The differential equation in which only rectilinear motions exit
b. The differential equation in which only angular motions exit
c. The differential equation in which both rectilinear and angular motions exit
d. None of the above
Answer  Explanation  Related Ques

ANSWER: The differential equation in which both rectilinear and angular motions exit

Explanation:
No explanation is available for this question!


35)   The motion of a system executing harmonic motion with one natural frequency is known as _______

a. principal mode of vibration
b. natural mode of vibration
c. both a. and b.
d. none of the above
Answer  Explanation  Related Ques

ANSWER: both a. and b.

Explanation:
No explanation is available for this question!