Science

Difference between angle of friction and angle of repose

Main difference

Both terms, angle of friction and angle of repose, are widely used in fields such as statics and dynamics, and especially in the field of mechanical engineering. Both terms have friction interference and that is why the angle of friction is also known as the angle of repose. Although one who knows its definitions and use in different conditions can easily differentiate between the two terms. The angle of friction is the angle between the normal force (N) and the force (R) resulting from the normal force and friction, while the angle of repose is the angle of maximum slope, where a placed object is just beginning to slide In other words, we can say that it is that maximum angle where a body or object can lean from the horizontal without falling or collapsing.

Comparative chart

Friction angle Angle of repose
Definition The angle of friction is the angle between the normal force (N) and the resultant force (R) of the normal force and friction. The angle of repose is the angle of maximum slope, where a placed object is just beginning to slide.
Applicable The angle of friction is applicable between rigid surfaces. Angle of repose is used for inclined surfaces, especially granular materials in soil mechanics.
Angle Hypothetical angle Real angle

What is the angle of friction?

The angle of friction is the angle between the normal force (N) and the resultant force (R) of the normal force and friction. It is actually the hypothetical angle between the resultant force and the horizon. The angle of friction is reached when failure occurs in response to shear stress. When we talk about friction, here we are generally talking about dry friction which is subdivided into static friction and kinetic friction. To determine the value of the friction angle, an experiment is carried out. The equation F = µ R explains the angle of friction when the static friction that creates an obstacle in the motion of an object reaches the upper limit, µ is the coefficient of friction in the case and R is the normal force.

Angle of repose?

It is quite similar to friction angle in that it has friction interference and has the ability to make the object stand firm at the maximum angle without collapsing or falling. It is actually the angle from which the object could start to slide horizontally. We can define the angle of repose as the angle of maximum slope, where a placed object is just beginning to slide. Angle of repose refers to granular materials and other similar materials, as it is mainly used in soil mechanics. Sediment stones, sand, and snow are some of the granular materials used in soil mechanics that are placed at angles where the object prevents it from sliding downward. In our daily life, We can see Antlions using the concept of angle of repose as they make the pots in the sand to catch their prey. They set an angle where the other insect slithers down and traps them.

Angle of friction vs. angle of repose

  • The angle of friction is the angle between the normal force (N) and the resultant force (R) of the normal force and friction, while the angle of repose is the angle of maximum slope, where a placed object is just beginning to slide .
  • Angle of friction is applicable between rigid surfaces, while angle of repose is used for inclined surfaces, especially granular materials in soil mechanics.
  • The angle of repose has the actual angle, while the angle of friction is based on the hypothetical angle between the resultant force and the horizon.

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