Download GTU (Gujarat Technological University) BE/BTech (Bachelor of Engineering / Bachelor of Technology) 2019 Summer 6th Sem Old 161901 Dynamics Of Machinery Previous Question Paper
Seat No.: ________ Enrolment No.___________
GUJARAT TECHNOLOGICAL UNIVERSITY
BE - SEMESTER ?VI(OLD) ? EXAMINATION ? SUMMER 2019
Subject Code:161901 Date:27/05/2019
Subject Name: Dynamics Of Machinery
Time:10:30 AM TO 01:00 PM Total Marks: 70
Instructions:
1. Attempt all questions.
2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.
Q.1 (a) Define the following terms:
(i) Periodic motion (ii) Simple Harmonic Motion (iii) Degree of Freedom(iv)
Natural Frequency (v) Damping Factor (vi) Logarithmic Decrement
(vii) Resonance
07
(b) The measurements on a mechanical vibrating system show that it has a
mass of 8 kg and that the springs can be combined to give an equivalent spring
of stiffness 5.4 N/mm. If the vibrating system have a dashpot attached which
exerts a force of 40 N when the mass has a velocity of 1 m/s, find : 1. critical
damping coefficient, 2. damping factor, 3. Logarithmic decrement, and 4. ratio
of two consecutive amplitudes.
07
Q.2 (a) Why Reciprocating masses are partially balanced. What are its effects.
07
(b)
Derive an expression for logarithmic decrement. What is the significance of
Logarithmic decrement?
07
OR
(b) Derive the governing equation characterizing the motion of free-damped
system.Also explain the terms ?under-damping?, ?over-damping? and ?critical
damping?.
07
Q.3 (a) Draw and explain the single and two node vibrations of three rotor system. 07
(b) Derive an expression for critical speed of a shaft carrying rotor and without
damping.
07
OR
Q.3 (a) Derive the expression to determine the natural frequency of free torsional
vibrations of a ?geared system? in standard notations.
07
(b) The mass of an electric motor is 120 kg and it runs at 1500 r.p.m. The
armature mass is 35 kg and its C.G. lies 0.5 mm from the axis of rotation. The
motor is mounted on five springs of negligible damping so that the force
transmitted is one-eleventh of the impressed force. Assume that the mass of the
motor is equally distributed among the five springs.Determine : 1. stiffness of
each spring; 2. dynamic force transmitted to the base at the operating speed; and
3. natural frequency of the system.
07
Q.4 (a) A, B, C and D are four masses carried by a rotating shaft at radii 100,125, 200
and 150 mm respectively. The planes in which the masses revolve are spaced
600 mm apart and the mass of B, C and D are 10 kg, 5 kg, and 4 kg respectively.
Find the required mass A and the relative angular settings of the four masses so
that theshaft shall be in complete balance.
07
(b) Discuss the balancing of V-engines. 07
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1
Seat No.: ________ Enrolment No.___________
GUJARAT TECHNOLOGICAL UNIVERSITY
BE - SEMESTER ?VI(OLD) ? EXAMINATION ? SUMMER 2019
Subject Code:161901 Date:27/05/2019
Subject Name: Dynamics Of Machinery
Time:10:30 AM TO 01:00 PM Total Marks: 70
Instructions:
1. Attempt all questions.
2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.
Q.1 (a) Define the following terms:
(i) Periodic motion (ii) Simple Harmonic Motion (iii) Degree of Freedom(iv)
Natural Frequency (v) Damping Factor (vi) Logarithmic Decrement
(vii) Resonance
07
(b) The measurements on a mechanical vibrating system show that it has a
mass of 8 kg and that the springs can be combined to give an equivalent spring
of stiffness 5.4 N/mm. If the vibrating system have a dashpot attached which
exerts a force of 40 N when the mass has a velocity of 1 m/s, find : 1. critical
damping coefficient, 2. damping factor, 3. Logarithmic decrement, and 4. ratio
of two consecutive amplitudes.
07
Q.2 (a) Why Reciprocating masses are partially balanced. What are its effects.
07
(b)
Derive an expression for logarithmic decrement. What is the significance of
Logarithmic decrement?
07
OR
(b) Derive the governing equation characterizing the motion of free-damped
system.Also explain the terms ?under-damping?, ?over-damping? and ?critical
damping?.
07
Q.3 (a) Draw and explain the single and two node vibrations of three rotor system. 07
(b) Derive an expression for critical speed of a shaft carrying rotor and without
damping.
07
OR
Q.3 (a) Derive the expression to determine the natural frequency of free torsional
vibrations of a ?geared system? in standard notations.
07
(b) The mass of an electric motor is 120 kg and it runs at 1500 r.p.m. The
armature mass is 35 kg and its C.G. lies 0.5 mm from the axis of rotation. The
motor is mounted on five springs of negligible damping so that the force
transmitted is one-eleventh of the impressed force. Assume that the mass of the
motor is equally distributed among the five springs.Determine : 1. stiffness of
each spring; 2. dynamic force transmitted to the base at the operating speed; and
3. natural frequency of the system.
07
Q.4 (a) A, B, C and D are four masses carried by a rotating shaft at radii 100,125, 200
and 150 mm respectively. The planes in which the masses revolve are spaced
600 mm apart and the mass of B, C and D are 10 kg, 5 kg, and 4 kg respectively.
Find the required mass A and the relative angular settings of the four masses so
that theshaft shall be in complete balance.
07
(b) Discuss the balancing of V-engines. 07
2
OR
Q.4 (a) Derive the following expressions, for an uncoupled two cylinder
locomotivengine:
1) Variation in tractive force;
2) Swaying couple; and
3) Hammer blow.
07
(b) Explain the ?direct and reverse crank? method for determining unbalanced
forces in radial engines.
07
Q.5 (a) Explain Vibration isolation and transmissibility
07
(b) Write step by step procedure of Stodola?s method to find out fundamental
natural frequency of system having three degree of freedom.
07
OR
Q.5 (a) Write a short note on vibration isolations.
07
(b) Describe Dunkerley?s method to find the natural frequency of a shaft
carryinseveral loads.
07
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This post was last modified on 20 February 2020