# Machine Kinematics Questions and Answers – Friction Between Lubricated Surfaces

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This set of Machine Kinematics Multiple Choice Questions & Answers (MCQs) focuses on “Friction Between Lubricated Surfaces”.

1. _____________ is the friction, experienced by a body, due to the motion of rotation as in case of foot step bearings.
a) Pivot friction
b) Solid friction
c) Dry friction
d) None of the mentioned

Explanation: Pivot friction is the friction, experienced by a body, due to the motion of rotation as in case of foot step bearings.

2. ______________ is the friction experienced between two dry and unlubricated surfaces in contact.
a) Pivot friction
b) Solid friction
c) Boundary friction
d) None of the mentioned

Explanation: The friction experienced between two dry and unlubricated surfaces in contact is known as dry or solid friction. It is due to the surface roughness.

3. ______________ is the friction, experienced between the rubbing surfaces, when the surfaces have a very thin layer of lubricant.
a) Pivot friction
b) Solid friction
c) Boundary friction
d) None of the mentioned

Explanation: Boundary friction It is the friction, experienced between the rubbing surfaces, when the surfaces have a very thin layer of lubricant. The thickness of this very thin layer is of the molecular dimension.

4. _____________ is the friction, experienced between the rubbing surfaces, when the surfaces have a thick layer of the lubricant.
a) Fluid friction
b) Solid friction
c) Boundary friction
d) None of the mentioned

Explanation: Fluid friction is the friction, experienced between the rubbing surfaces, when the surfaces have a thick layer of the lubricant. In this case, the actual surfaces do not come in contact and thus do not rub against each other.

5. _____________ is a measure of the resistance offered to the sliding one layer of the lubricant over an adjacent layer.
a) Viscocity
b) Density
c) Oiliness
d) None of the mentioned

Explanation: The viscosity is a measure of the resistance offered to the sliding one layer of the lubricant over an adjacent layer.

6. The absolute viscosity of a lubricant may be defined as the force required to cause a plate of unit area to slide with unit velocity relative to a parallel plate.
a) True
b) False

Explanation: The absolute viscosity of a lubricant may be defined as the force required to cause a plate of unit area to slide with unit velocity relative to a parallel plate, when the two plates are separated by a layer of lubricant of unit thickness.

7. The lubricant which gives ______________ force of friction is said to have greater oiliness.
a) greater
b) lesser
c) similar
d) none of the mentioned

Explanation: The lubricant which gives lower force of friction is said to have greater oiliness.

8. When the lubricants are smeared on two different surfaces, it is found that the force of friction with one lubricant is different than that of the other.
a) True
b) False

Explanation: When these lubricants are smeared on two different surfaces, it is found that the force of friction with one lubricant is different than that of the other. This difference is due to the property of the lubricant known as oiliness.

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