Difference Between Angle of Friction and Angle of Repose

Angle of Friction vs Angle of Repose

Angle of friction and angle of repose are two very important quantities measured in friction. These two quantities hold a great significance in fields such as statics and dynamics of solid bodies and statics of granules. In this article, we are going to discuss what angle of friction and angle of repose are, their definitions, applications of these angles, the similarities and finally the difference between angle of friction and angle of repose.

What is Angle of Friction?

Friction is probably the most common resistive force we experience every day. Friction is caused by the contact of two rough surfaces. Friction has five modes. Dry friction occurs between two solid bodies; fluid friction is also known as viscosity; lubricated friction where two solids are separated by a liquid layer; skin friction opposes a moving solid in a liquid, and internal friction causes the internal components of a solid to make friction. However, the term “friction” is most commonly used in place of the dry friction. This is caused by the rough microscopic cavities on each of the surfaces fitting each other and refusing to move. The dry friction between two surfaces depends on the friction coefficient and the reactive force normal to the plane acting on the object. The maximum static friction between two surfaces is just a bit higher than the dynamic friction. Since, for a given two solid surfaces, the friction only depends on the reactive force between the two surfaces, the equation F = µ R can be obtained. It must be noticed that the friction is independent of the contact area of two surfaces. If the term µ is written as angle Tan (θ), then θ is defined as the angle of friction between the two surfaces. Since Tan (θ) is equal to the ratio of F to R, the angle θ is the angle between the horizontal line and the resultant force of F and R.

What is Angle of Repose?

Angle of repose is a property of granular materials, which is connected to friction. The angle of repose is the steepest angle of descent or dip of the slope relative to the horizontal plane, when material on the slope face is on the verge of sliding. This angle can theoretically take values from 0 degrees to 90 degrees. The angle of repose is a very important property for granular materials since it decides how high and how wide a material will spread. Snow, sand and sediment stones can be taken as such materials. The angle of repose is directly dependent on the maximum angle of friction of the material.

What is the difference between angle of repose and angle of friction? • Angle of friction is defined for solid materials with rigid bodies. Angle of repose is defined to granular materials only. • Angle of friction is a hypothetical angle between the resultant force and the horizon. Angle of repose is a real angle, which can be measured.