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Friction vs. Viscosity: What's the Difference?

Edited by Janet White || By Harlon Moss || Published on January 28, 2024
Friction is the resistance to motion between two contacting surfaces, while viscosity is the measure of a fluid's resistance to flow.

Key Differences

Friction occurs between two solid surfaces in contact, resisting their relative motion. Viscosity, however, describes a fluid's internal resistance to flow under an applied force.
The cause of friction lies in the surface roughness and interlocking of particles between solids. Viscosity is determined by the molecular composition and interactions within a fluid.
Friction results in the conversion of kinetic energy to heat. In contrast, viscosity influences the rate at which fluid flows and its behavior under stress.
Friction is influenced by factors like surface texture, normal force, and material types. Viscosity is affected by temperature, pressure, and the fluid's composition.
In practical applications, reducing friction is often desirable to decrease wear and energy loss, while manipulating viscosity is crucial in processes like lubrication and material transport.

Comparison Chart


Resistance between solid surfaces
Fluid’s internal flow resistance


Surface roughness, interlocking
Molecular composition, interaction

Energy Conversion

Converts kinetic energy to heat
Affects flow rate and behavior

Influencing Factors

Surface texture, force, material
Temperature, pressure, composition

Practical Importance

Minimizing wear and energy loss
Important in lubrication, transport

Friction and Viscosity Definitions


Force opposing the relative movement of solid surfaces.
Friction in the engine causes it to heat up.


Depends on intermolecular forces within a fluid.
Glycerin’s high viscosity is due to strong intermolecular forces.


A phenomenon converting kinetic energy to thermal energy.
Friction heats up the brakes when applied.


Altered by changes in temperature and pressure.
Viscosity of gases increases with temperature.


Influenced by the normal force exerted.
Increasing the weight on the object increases friction.


Measure of a fluid's resistance to flow.
Honey has a higher viscosity than water.


Dependent on surface roughness and material type.
Friction is less on smooth surfaces.


A fluid's internal friction affecting its flow.
The viscosity of oil decreases with heating.


Resistance to motion between contacting surfaces.
Friction between the tire and road provides grip.


Critical in applications like lubrication and hydraulics.
Proper viscosity is essential for effective lubrication.


The rubbing of one object or surface against another.


The condition or property of being viscous.


Conflict, as between persons having dissimilar ideas or interests; clash.


(Physics) Coefficient of viscosity.


(Physics) A force that resists the relative motion or tendency to such motion of two bodies or substances in contact.


(uncountable) The state of being viscous.


The rubbing of one object or surface against another.


A quantity expressing the magnitude of internal friction in a fluid, as measured by the force per unit area resisting uniform flow.


(physics) A force that resists the relative motion or tendency to such motion of two bodies in contact.


A tendency to prolong interpersonal encounters.


Massage of the body to restore circulation.


The quality or state of being viscous.


(figuratively) Conflict, as between persons having dissimilar ideas or interests; clash.


A property possessed by a viscous fluid, being a resistance to the forces causing a fluid to flow, caused by interactions between the molecules of the fluid and between the fluid and the walls of the conduit through which it moves; also, a measure of such a property.


(Second Sino-Japanese War) Conflict, as between the Communists and non-Hanjian Kuomintang forces.


Resistance of a liquid to sheer forces (and hence to flow)


The act of rubbing the surface of one body against that of another; attrition; in hygiene, the act of rubbing the body with the hand, with flannel, or with a brush etc., to excite the skin to healthy action.


The resistance which a body meets with from the surface on which it moves. It may be resistance to sliding motion, or to rolling motion.


A clashing between two persons or parties in opinions or work; a disagreement tending to prevent or retard progress.


A state of conflict between persons


The resistance encountered when one body is moved in contact with another


Effort expended in rubbing one object against another


What is friction?

Resistance to motion between two contacting surfaces.

What is viscosity?

A measure of a fluid’s resistance to flow.

Where does friction occur?

Between solid surfaces in contact.

What determines viscosity?

Molecular composition and interactions.

Where is viscosity observed?

In fluids, both liquids and gases.

How is friction useful?

It provides grip and control in movement.

Does friction produce heat?

Yes, it converts kinetic energy to heat.

What is the unit of friction?

Newtons (N) as it’s a force.

What causes friction?

Surface roughness and interlocking of particles.

Can friction be eliminated?

Not entirely, but it can be reduced.

Is friction always desirable?

Not always, as it can cause wear and energy loss.

What is the unit of viscosity?

Pascal-seconds (Pa.s) or poise.

Are there types of friction?

Yes, including static, sliding, and rolling friction.

Is viscosity affected by flow speed?

In Newtonian fluids, it’s not; in non-Newtonian fluids, it is.

Why is viscosity important?

It influences fluid flow in systems like lubrication.

Does viscosity generate heat?

No, it does not generate heat.

Can viscosity be controlled?

Yes, through temperature, pressure, and additives.

Does temperature affect viscosity?

Yes, typically viscosity decreases with increasing temperature.

Are there types of viscosity?

Yes, dynamic (absolute) and kinematic viscosity.

Is friction a vector quantity?

Yes, it has both magnitude and direction.
About Author
Written by
Harlon Moss
Harlon is a seasoned quality moderator and accomplished content writer for Difference Wiki. An alumnus of the prestigious University of California, he earned his degree in Computer Science. Leveraging his academic background, Harlon brings a meticulous and informed perspective to his work, ensuring content accuracy and excellence.
Edited by
Janet White
Janet White has been an esteemed writer and blogger for Difference Wiki. Holding a Master's degree in Science and Medical Journalism from the prestigious Boston University, she has consistently demonstrated her expertise and passion for her field. When she's not immersed in her work, Janet relishes her time exercising, delving into a good book, and cherishing moments with friends and family.

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