# Mechanical Vibrations Questions and Answers – Damping Elements

This set of Mechanical Vibrations Multiple Choice Questions & Answers (MCQs) focuses on “Damping Elements”.

1. When do the viscous damping occurs in a mechanical system?
a) when the system is in contact with a non viscous liquid
b) when the system is in contact with a solid material
c) when the system is in contact with another mechanical system
d) when the system is in contact with a viscous liquid

Explanation: Viscous damping is added to mechanical system as a means of vibration control. It occurs in mechanical system, when it is contact with viscous liquid.

2. Damping force in viscous damping is proportional to————– of the vibrating body
a) Displacement
b) Velocity
c) Stiffness
d) Frequency

Explanation: The damping force in viscous damping is usually proportional to the velocity.F= cv, where c is Viscous damping coefficient.

3. The amount of energy dissipated in vibrating body due to viscous damping depends on shape of the vibrating body
a) Yes
b) False

Explanation: The energy dissipated in vibrating body depends on size and shape, viscosity of the fluid, frequency of the vibration and the velocity of the vibrating body.

4. What is the reason for dry friction damping in a mechanical system ?
a) due to friction between rubbing surfaces
b) due to sufficient lubrication between rubbing surfaces
c) due to high stresses induced in the mechanical system
d) due to imbalance in mechanical system

Explanation: In this dry friction damping, damping force is opposite to the motion of vibrating body. It is caused due to friction between rubbing surfaces that have insufficient lubrication.

5. What is c in following figure ?

a) Spring
b) Dashpot
c) Beam
d) Capacitor

Explanation: c in above figure is dashpot. A dashpot is added to mechanical systems to provide viscous damping.

6. In the following figure a is the free body diagram of b

a) Yes
b) No

Explanation: b is the free body diagram of a. The free body diagram of a rigid body shows the viscous force in the opposite direction of the positive velocity.

7. The force developed in the dashpot ————

a) is not equal to the force from damper on the body
b) is not considered in the analysis of system
c) is equal to the force from damper on the body
d) is infinite

Explanation: The force developed in the dashpot is equal to and opposite of the force from the damper on the body.

8. A disk rotates in a dish of a viscous liquid, producing a moment acts as ———————-
a) Viscous damper
b) Torsional Viscous damper
c) Damper
d) Non viscous damper

Explanation: A net moment due to the shear stress developed on the face of the disk acts as torsional viscous damper.

9. The moment produced in the rotating disk of a viscous liquid is proportional————–
a) to the velocity of the shaft
b) to the angular velocity of the shaft
c) to the viscosity of the fluid
d) to velocity of the fluid

Explanation: The moment produced in the rotating disk of a viscous liquid is proportional to the angular velocity of the shaft. M = ctѳ , where ct is the torsional viscous damping coefficient.

10. Viscous damping can be produced by a body moving through a magnetic field
a) Yes
b) No

Explanation: Viscous damping can be produced by a body oscillating on the surface of a lake, or by the oscillations of a column of liquid in a U-tube manometer, or by a body moving through a magnetic field.

Sanfoundry Global Education & Learning Series – Mechanical Vibrations.

To practice all areas of Mechanical Vibrations, here is complete set of Multiple Choice Questions and Answers.

If you find a mistake in question / option / answer, kindly take a screenshot and email to [email protected]