# Machine Dynamics Questions and Answers – Frequency of Free Damped Vibrations

This set of Machine Dynamics Multiple Choice Questions & Answers (MCQs) focuses on “Frequency of Free Damped Vibrations”.

1. Fluid resistance causes damping which is known as ______
a) Resistance damping
b) Fluid damping
c) Viscous damping
d) Liquid damping

Explanation: Damping due to the resistance offered by the fluid is known as viscous damping. This is because of the reduction in the amplitude caused by the viscous forces of the fuild.

2. In damped vibrations, the amplitude of the resulting vibration gradually diminishes.
a) True
b) False

Explanation: Since a certain amount of energy is always dissipated while overcoming the resistance forces, In damped vibrations, the amplitude of the resulting vibration gradually diminishes.

3. In damped vibrations, the amplitude of the resulting vibration gradually reduces. This is due to the reason that an amount of energy is always dissipated to overcome the ________
a) Frictional resistance
b) Work done
c) Fluid pressure
d) Air pressure

Explanation: In case of damped vibrations, the amplitude of the resulting vibration gradually diminishes. This is due to the reason that a certain amount of energy is always dissipated to overcome the frictional resistance.

4. The resistance to the motion of the body is provided by ______
a) Medium of vibration
b) Speed of vibration
c) Length of the material
d) External friction

Explanation: The resistance to the motion of the vibrating body is provided partly by the medium in which the vibration takes place and partly by the internal friction.

5. In which direction does the damping force acts?
a) Opposite to the motion
b) Along the motion
c) Perpendicular to motion
d) Variable

Explanation: It is assumed that the frictional resistance to the motion of the body is directly proportional to the speed of, therefore Damping force or frictional force on the mass acts in opposite direction to the motion of the mass.

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6. In which direction does the accelerating force acts?
a) Opposite to the motion
b) Along the motion
c) Perpendicular to motion
d) Variable

Explanation: It is assumed that the frictional resistance to the motion of the body is directly proportional to the speed, therefore accelerating force on the mass acts in same direction to the motion of the mass.

7. In which of the following cases, overdamping occurs?
a) Roots are real
b) Roots are complex conjugate
c) Roots are equal
d) Independent of the equation

Explanation: If the roots k1 and k2 are real but negative the case is of overdamping or large damping and the mass moves slowly to the equilibrium position. This motion is known as aperiodic.

8. In which of the following cases, underdamping occurs?
a) Roots are real
b) Roots are complex conjugate
c) Roots are equal
d) Independent of the equation

Explanation: If the roots k1 and k2 are complex, the case is of underdamping or small damping and the mass moves slowly to the equilibrium position.

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