Engineering Questions with Answers - Multiple Choice Questions
Machine Dynamics MCQ – Damping Factor & Magnification Factor
1 - Question
The ratio of the actual damping coefficient (c) to the critical damping coefficient (cc ) is known as _________
a) Damping factor
b) Damping coefficient
c) Resistive factor
d) Resistive coefficient
View Answer
Answer: a
Explanation: The ratio of the actual damping coefficient (c) to the critical damping coefficient (cc) is known as damping factor or damping ratio given by c/Cc.
2 - Question
Calculate critical damping coefficient in Ns/m from the following data.
mass = 200Kg
ω = 20rad/s
a) 25,132
b) 26,132
c) 27,132
d) Not possible
View Answer
Answer: d
Explanation: We know that critical damping coefficient is given by the relation
Cc = 2πxmxω
inserting the values we get
Cc = 25132 N/m/s
The above value is in N/m/s and damping factor cannot be calculated in Ns/m.
3 - Question
Calculate critical damping coefficient in N/m/s from the following data:
mass = 100Kg
ω = 40rad/s
a) 25,132
b) 26,132
c) 27,132
d) 28,132
View Answer
Answer: a
Explanation: We know that critical damping coefficient is given by the relation
Cc = 2πxmxω
inserting the values we get
Cc = 25132 N/m/s.
4 - Question
Calculate critical damping coefficient in N/m/s from the following data:
mass = 100Kg
ω = 10rad/s
a) 5,132
b) 6,283
c) 7,132
d) 8,132
View Answer
Answer: a
Explanation: We know that critical damping coefficient is given by the relation
Cc = 2πxmxω
inserting the values we get
Cc = 6283 N/m/s.
5 - Question
Calculate damping ratio from the following data:
mass = 200Kg
ω = 20rad/s
damping coefficient = 800 N/m/s
a) 0.03
b) 0.04
c) 0.05
d) 0.06
View Answer
Answer: a
Explanation: We know that critical damping coefficient is given by the relation
Cc = 2πxmxω
inserting the values we get
Cc = 25132 N/m/s
ratio = 800/25132.
6 - Question
Calculate damping ratio from the following data:
mass = 200Kg
ω = 20rad/s
damping coefficient = 1000 N/m/s
a) 0.03
b) 0.04
c) 0.05
d) 0.06
View Answer
Answer: b
Explanation: We know that critical damping coefficient is given by the relation:
Cc = 2πxmxω
inserting the values we get
Cc = 25132 N/m/s
ratio = 1000/25132 = 0.04.
7 - Question
Unit of damping factor is N/m/s.
a) True
b) False
View Answer
Answer: b
Explanation: Damping factor is a ratio of damping coefficient to the critical damping coefficient hence, it has no unit and is a dimensionless quantity.
8 - Question
Magnification factor is the ratio of the maximum displacement due to forced vibrations to the deflection due to _______
a) Static force
b) Dynamic force
c) Torsion
d) Compression
View Answer
Answer: a
Explanation: Magnification factor or the Dynamic magnifier is the ratio of maximum displacement of the forced vibration to the deflection due to the static force.
9 - Question
Maximum displacement due to forced vibration is dependent on deflection due to static force.
a) True
b) False
View Answer
Answer: a
Explanation: Maximum displacement due to forced vibration is directly proportional to the displacement due to static force, hence it is dependent on deflection due to static force.
10 - Question
In which of the cases the factor c = 0?
a) When there is damping
b) No damping
c) Resonance
d) c is never 0
View Answer
Answer: b
Explanation: When there is no damping, the factor c becomes 0 and magnification factor becomes independent of the damping coefficient.
11 - Question
A body of mass 20 kg is suspended from a spring which deflects 20mm under this load. Calculate the frequency of free vibrations in Hz.
a) 3.5
b) 5
c) 6
d) 7
View Answer
Answer: a
Explanation: Frequency of free vibrations is given by (1/2π)√(g/d)
substituting the value, we get
f = 3.5 Hz.
12 - Question
If the mass increases, then the frequency of the free vibrations increases.
a) True
b) False
View Answer
Answer: b
Explanation: Frequency of free vibrations is given by (1/2π)√(g/d), from the given formula it is evident that it is independent of mass, Hence the given statement is false.