MCQOPTIONS
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MCQOPTIONS
This section includes 15 Mcqs, each offering curated multiple-choice questions to sharpen your Mechanical Vibrations knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
A mass m attached to a spring is subjected to a harmonic force as shown in figure. The amplitude of the forced motion is observed to be 50 mm. the value of m (in kg) is |
| A. | 0.1 |
| B. | 1 |
| C. | 0.3 |
| D. | 0.5 |
| Answer» B. 1 | |
| 2. |
In vibration isolation, which one of the following statements is NOT correct regarding Transmissibility (T)? |
| A. | T is nearly unity at small excitation frequencies |
| B. | T can be always reduced by using higher damping at any excitation frequency |
| C. | T is unity at the frequency ratio of √2 |
| D. | T is infinity at resonance for undamped systems |
| Answer» C. T is unity at the frequency ratio of √2 | |
| 3. |
In vibration isolation if ω/ωn is less than √2 then the transmissibility will be |
| A. | Less than one |
| B. | Equal to one |
| C. | Greater than one |
| D. | Zero |
| Answer» D. Zero | |
| 4. |
In the viscous damped vibration, the logarithmic decrement value over five cycles is found to be 8.11. What is viscous damping factor of vibratory system? |
| A. | 20% |
| B. | 25% |
| C. | 30% |
| D. | 15% |
| Answer» C. 30% | |
| 5. |
For effective vibration isolation, the frequency ratio \(\frac{\omega_n}{\omega}\) must be: |
| A. | equal to \(\frac{1}{\sqrt2}\) |
| B. | more than \(\frac{1}{\sqrt2} \) |
| C. | less than \(\frac{1}{\sqrt2}\) |
| D. | less than \(\frac{5}{\sqrt2}\) |
| Answer» D. less than \(\frac{5}{\sqrt2}\) | |
| 6. |
A single degree of freedom system having mass 1 kg and stiffness 10 kN/m initially at rest is subjected to an impulse force of magnitude 5 kN for 10-4 seconds. The amplitude in mm of the resulting free vibration is |
| A. | 0.5 |
| B. | 1 |
| C. | 5 |
| D. | 10 |
| Answer» D. 10 | |
| 7. |
In a forced vibration system, for which value of frequency ratio (ωf/ωn), the transmissibility is same for all the values of damping factors |
| A. | 1 |
| B. | 2 |
| C. | √2 |
| D. | 1/2 |
| Answer» D. 1/2 | |
| 8. |
A machine of 250 kg mass is supported on springs of total stiffness 100 kN/m. Machine has an unbalanced rotating force of 350 N at speed of 3600 rpm. Assuming a damping factor of 0.15, the value of transmissibility ratio is: |
| A. | 0.0531 |
| B. | 0.9922 |
| C. | 0.0162 |
| D. | 0.0028 |
| Answer» D. 0.0028 | |
| 9. |
A machine of mass 100 kg is subjected to an external harmonic force with a frequency of 40 rad/s. The designer decides to mount the machine on an isolator to reduce the force transmitted to the foundation. The isolator can be considered as a combination of stiffness (K) and damper (damping factor, ζ) in parallel. The designer has the following four isolators:1) k = 640 kN/m, ζ = 0.70 2) k = 640 kN/m, ζ = 0.073) k = 22.5 kN/m, ζ = 0.704) k = 22.5 kN/m, ζ = 0.07Arrange the isolators in the ascending order of the force transmitted to the foundation. |
| A. | 4-3-1-2 |
| B. | 3-1-2-4 |
| C. | 1-3-2-4 |
| D. | 1-3-4-2 |
| Answer» B. 3-1-2-4 | |
| 10. |
A single-degree freedom spring-mass system is subjected to a sinusoidal force of 10 N amplitude and frequency ω along the axis of the spring. The stiffness of the spring is 150 N/m, damping factor is 0.2 and the undamped natural frequency is10ω At steady state, the amplitude of vibration (in m) is approximately |
| A. | 0.05 |
| B. | 0.07 |
| C. | 0.70 |
| D. | 0.90 |
| Answer» C. 0.70 | |
| 11. |
A vehicle suspension system consists of a spring and a damper. The stiffness of the spring is 3.6 kN/m and the damping constant of the damper is 400 Ns/m. If the mass is 50 kg, then the damping factor ζ and damped natural frequency (fd), respectively, are |
| A. | 0.471 and 1.19 Hz |
| B. | 0.471 and 7.48 Hz |
| C. | 0.666 and 1.35 Hz |
| D. | 0.666 and 8.50 Hz |
| Answer» B. 0.471 and 7.48 Hz | |
| 12. |
A body of mass 100 kg with natural frequency 10 rad/sec has critical damping: |
| A. | 100 N/m/sec |
| B. | 2000 N/m/sec |
| C. | 3142 N/m/sec |
| D. | 10 N/m/sec |
| Answer» C. 3142 N/m/sec | |
| 13. |
Consider the following statements. Transmissibility of vibrations(1) Is more than 1, when ω/ωn √2 (3) Increases as the damping is increased |
| A. | 1, 2 and 3 |
| B. | 1 and 2 only |
| C. | 2 and 3 only |
| D. | 1 and 3 only |
| Answer» C. 2 and 3 only | |
| 14. |
A single-degree-of freedom oscillator is subjected to harmonic excitation F(t) = F0 cos(ωt) as shown in the figure.The non-zero value of ω, for which the amplitude of the force transmitted to the ground will be F0, is |
| A. | \(\sqrt {\frac{k}{{2m}}}\) |
| B. | \(\sqrt {\frac{k}{m}}\) |
| C. | \(\sqrt {\frac{{2k}}{m}}\) |
| D. | \(2\sqrt {\frac{k}{m}}\) |
| Answer» D. \(2\sqrt {\frac{k}{m}}\) | |
| 15. |
For a vibrating system, the successive amplitudes of vibration obtained under free effects are 0.70, 0.28, 0.25, 0.23, and 0.067 respectively. The value of the damping ratio of the system is given by: |
| A. | 9.28 |
| B. | 0.0928 |
| C. | 0.00928 |
| D. | 0.928 |
| Answer» C. 0.00928 | |