Solid Friction and Viscosity Similarities & Dissimilarities

Solid Friction and Viscosity

Both the terms are very important. It is very necessary to understand friction and viscosity in an easy and proper way. We will discuss these terms in a very simple way in this post.

What is Friction?

Friction is the force that opposes the motion. It acts between the surfaces in contact.

Friction plays a very important part in our life. It is called a necessary evil. Friction has both advantages and disadvantages.

The advantage of friction is that it helps in writing, walking, running, applying brakes, holding things, and many others. The disadvantage of friction is that it generates a lot of heat in machines, causes wear and tear, decreases the efficiency of machines, etc.

There are basically four types of friction-

  • Static Friction: When a body is at rest
  • Sliding: when a body slides over another body.
  • Rolling Friction: When a body rolls over another body.
  • Fluid Friction: When a body moves in a fluid (liquid, gas).

Causes of Friction

The main causes of friction are due to the surface roughness or irregularities of the surfaces in contact. The other factor is the force of attraction between the molecules of the surfaces in contact.

Definition of Solid Friction

The friction that acts between the surfaces of solid surfaces.


It refers to the force that opposes the relative motion between two solid objects in contact. It is the resistance encountered when an object or a body tries to slide, push, or move across another body or object.

The types of friction such as Static, Sliding, and Rolling friction are such examples.

Viscosity Definition

It is the internal friction of fluid flow. It is the measure of fluid’s resistance to flow.

Dissimilarities of Solid Friction and Viscosity

Let us look at the differences or dissimilarities-

  • Viscous force is directly proportional to the relative velocity of the layers of liquid under consideration whereas Friction is independent of the relative velocity of bodies in contact.
  • Viscosity is proportional to the surface area of contact of liquid layers whereas friction is independent of the area of surfaces in contact.
  • Viscosity does not depend on the normal reaction between the two layers in contact but friction does.

Similarities Friction Viscosity

Let us now look at the similarities of Friction and Viscosity.

  • Both oppose the motion.
  • Both act tangentially in the opposite direction of motion.
  • They are the result of intermolecular forces.
  • Both oppose the motion.

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