Download PTU B.Tech 2021 Jan ME 7th Sem 71996 Mechanical Vibrations Question Paper

Roll No.

Total No. of Questions : 18

Total No. of Pages : 02

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B.Tech. (Mechanical Engineering) (Sem.-7)

MECHANICAL VIBRATIONS

Subject Code : BTME-803

M.Code: 71996

Time : 3 Hrs.

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Max. Marks : 60

INSTRUCTIONS TO CANDIDATES :

1. SECTION-A is COMPULSORY consisting of TEN questions carrying TWO marks each.
2. SECTION-B contains FIVE questions carrying FIVE marks each and students have to attempt any FOUR questions.
3. SECTION-C contains THREE questions carrying TEN marks each and students have to attempt any TWO questions.

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SECTION-A

Write briefly :

1. Differentiate Oscillation and Vibration.
2. In short define types of Vibrations.
3. Describe causes of vibrations.

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4. Vibration is a necessary Evil. Explain.
5. What are various effects of vibrations? Explain.
6. What do you understand by Natural frequency?
7. With help of Figure explain multi-degree freedom system.
8. What do you understand by degrees of freedom?

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9. Why soldiers are asked to break their steps while crossing a bridge? Explain.
10. What is the principle of vibration absorber? Explain with help of neat sketch.

SECTION-B

11. A spring mass system with mass m kg and stiffness k N/m has a natural frequency of 1 Hz. Determine the value of stiffness k1 of another spring which when arranged in conjunction with spring of stiffness k in series will lower the natural frequency by 20% and in parallel will raise the natural frequency by 20%.
12. Describe and differentiate Coulomb and Viscous Damping in detail.

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13. Add two harmonic motions analytically which are represented by the equations :
    x(1) = 4 sin (7t+π/6)
    x(2) = 5 cos(7t-π/12)
    Compare the result with graphical representation.
14. Torque T is applied at the midpoint of a uniform cross-section circular shaft of length ‘l', which twists the shaft by angle a radians. If the torque is released suddenly, derive equation for resulting motion.

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15. Describe torsional vibration absorber with neat sketch.

SECTION-C

16. Explain the following :
    1. Vibration isolation transmissibility
    2. Torsional vibration of circular shafts

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17. A beam having length of 0.42 m, moment of inertia 10000m² and modulus of elasticity 196000 N/m² is supporting two masses 40 kg and 20 kg at a distance of 0.16 and 0.24 m from one end. Determine lowest natural frequency by Rayleigh's method.
18. Determine the normal function for the boundary conditions as one end fixed and the other end free of a cantilever system of length ‘l', starting with the expression for strain energy during free longitudinal vibration of bar with uniform area of cross-section.

NOTE: Disclosure of Identity by writing Mobile No. or Making of passing request on any page of Answer Sheet will lead to UMC against the Student.

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