# Machine Kinematics Questions and Answers – Limiting Angle of Friction

This set of Machine Kinematics Multiple Choice Questions & Answers (MCQs) focuses on “Limiting Angle of Friction”.

1. When the rubbing surfaces are separated from each other by a very thin film of lubricant it is known as
a) kinetic friction
b) dry friction
c) boundary lubrication
d) none of the mentioned

Explanation: When the rubbing surfaces are separated from each other by a very thin film of lubricant it is known as boundary lubrication.
When the two solid surfaces sliding over each other are free from contaminating fluid or film, the resistance encountered is called dry friction.

2. Sliver sulphate, tungsten disulphide, graphite, molybdenum disulphide, lead oxide are examples of
a) boundary lubrication
b) viscous lubrication
c) solid lubrication
d) none of the mentioned

Explanation: Sliver sulphate, tungsten disulphide, graphite, molybdenum disulphide, lead oxide are examples of solid lubrication.
Step bearing is used to resist the end thrust of the shafts.

3. __________ is used to resist the end thrust of the shafts.
a) friction circle
b) step bearings
c) injector
d) none of the mentioned

Explanation: Step bearing is used to resist the end thrust of the shafts.

4. When the two solid surfaces sliding over each other are free from contaminating fluid or film, the resistance encountered is called
a) kinetic friction
b) dry friction
c) boundary lubrication
d) none of the mentioned

Explanation: When the two solid surfaces sliding over each other are free from contaminating fluid or film, the resistance encountered is called dry friction.
When the rubbing surfaces are separated from each other by a very thin film of lubricant it is known as boundary lubrication.

5. For design of ordinary machinery, value of journal friction can be taken as
a) 0.008 to 0.02
b) 0.07 to 0.15
c) 0.05 to 0.80
d) none of the mentioned

Explanation: For very low velocities of rotation, high loads, and with good lubrication can be taken as 0.07 to 0.15.
For design of ordinary machinery, value of journal friction can be taken as 0.008 to 0.02.

6. For very low velocities of rotation, high loads, and with good lubrication can be taken as
a) 0.008 to 0.02
b) 0.07 to 0.15
c) 0.05 to 0.80
d) none of the mentioned

Explanation: For very low velocities of rotation, high loads, and with good lubrication can be taken as 0.07 to 0.15.
For design of ordinary machinery, value of journal friction can be taken as 0.008 to 0.02.

7. When the lubrication is arranged so that rubbing surfaces are separated by a fluid film, and the load on the surfaces is carried entirely by the hydrostatic or hydrodynamic pressure in the film, it is known as
a) boundary lubrication
b) viscous lubrication
c) solid lubrication
d) none of the mentioned

Explanation: When the lubrication is arranged so that rubbing surfaces are separated by a fluid film, and the load on the surfaces is carried entirely by the hydrostatic or hydrodynamic pressure in the film, it is known as viscous lubrication.
When the rubbing surfaces are separated from each other by a very thin film of lubricant it is known as boundary lubrication.

8. When the load on the rubbing surfaces is carried partly by a fluid viscous film and partly by areas of boundary lubrication, it is known as
a) incomplete lubrication
b) viscous lubrication
c) solid lubrication
d) none of the mentioned

Explanation: When the lubrication is arranged so that rubbing surfaces are separated by a fluid film, and the load on the surfaces is carried entirely by the hydrostatic or hydrodynamic pressure in the film, it is known as viscous lubrication.
When the rubbing surfaces are separated from each other by a very thin film of lubricant it is known as boundary lubrication.
When the load on the rubbing surfaces is carried partly by a fluid viscous film and partly by areas of boundary lubrication, it is known as incomplete lubrication.

9. When effect of friction is negligible, the force is transmitted by the link from driver to the driven link through the centre line of the pins connecting the link. With friction, the line of action shifts and is tangent to _____________
a) kinetic friction
b) dry friction
c) friction circle
d) none of the mentioned

Explanation: When effect of friction is negligible, the force is transmitted by the link from driver to the driven link through the centre line of the pins connecting the link. With friction, the line of action shifts and is tangent to friction circle.
When the load on the rubbing surfaces is carried partly by a fluid viscous film and partly by areas of boundary lubrication, it is known as incomplete lubrication.

10. If one surface slides over the other, being pressed together by a normal force N, a frictional force F resisting the motion must be overcome. The ratio F/N is called ______________
a) kinetic friction
b) dry friction
c) friction circle
d) none of the mentioned

Explanation: If one surface slides over the other, being pressed together by a normal force N, a frictional force F resisting the motion must be overcome. The ratio F/N is called kinetic friction.
When the two solid surfaces sliding over each other are free from contaminating fluid or flim, the resistance encountered is called dry friction.

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