Angle of friction

Definition

Given two surfaces, the angle of repose between the two surfaces is defined as the angle $\theta$ that a fixed inclined plane made up of one surface must make with the horizontal so that a body with the second surfaces placed on it just starts slipping.

This angle is numerically given by:

$\!\theta =\tan ^{-1}(\mu _{s})$

where $\mu _{s}$ is the limiting coefficient of static friction.

It is numerically equal to the angle of friction.

For more information about motion on an inclined plane, refer sliding motion along an inclined plane.

External links

Instructional video links

• MIT OCW lecture on friction by Walter Lewin does not explicitly introduce the term "angle of repose" but derives the expression for it (time interval: 02:24 -- 08:58)