Download PTU (Punjab Technical University) B.Tech (Bachelor of Technology) / BE (Bachelor of Engineering) 2021 January ME 7th Sem 71996 Mechanical Vibrations Previous Question Paper

Total No. of Pages : 02

Total No. of Questions : 18

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

MECHANICAL VIBRATIONS

Subject Code : BTME-803

M.Code : 71996

Time : 3 Hrs. Max. Marks : 60

INST RUCT IONS T O CANDIDAT ES :

1 .

SECT ION-A is COMPULSORY cons is ting of TEN questions carrying TWO marks

each.

2 .

SECT ION-B c ontains F IVE questions c arrying FIVE marks eac h and s tud ents

have to atte mpt any FOUR q ues tions.

3 .

SECT ION-C contains THREE questions carrying T EN marks e ach and s tudents

have to atte mpt any T WO questio ns.

SECTION-A

Write briefly :

1)

Differentiate Oscillation and Vibration.

2)

In short define types of Vibrations.

3)

Describe causes of vibrations.

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?

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.

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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.

13) Add two harmonic motions analytically which are represented by the equations :

x(1) = 4 sin (7t+/6)

x(2) = 5 cos(7t-/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 radians. If the torque is released suddenly, derive equation

for resulting motion.

15) Describe torsional vibration absorber with neat sketch.

SECTION-C

16) Explain the following :

a) Vibration isolation transmissibility

b) Torsional vibration of circular shafts

17) A beam having length of 0.42 m, moment of inertia 10000m4 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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This post was last modified on 26 June 2021