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

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

Roll No.
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.
1 | M - 7 1 9 9 6
( S 2 ) - 6 0 3

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.
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