Difference between angle of friction and angle of repose

There are various concepts in Physics that are often confused with each other, one of these areas is friction. In this case, we want to talk about two important angles: the angle of friction and the angle of repose. Although they look similar, these terms are different. Here we explain what each of them consists of and why they are important.

Friction angle

We will start by talking about the angle of friction. This term refers to the maximum inclination that an object can have before it begins to slide on a surface. That is, it is the angle at which the friction force is unable to equal the gravitational force that pushes the object downward.

In other words, if an object is on an inclined plane and the angle of inclination is gradually increased, it will reach the angle of friction when it begins to move on its own. This angle varies depending on the nature of the surface and the material of the object in question.

It should be noted that the friction angle is not a fixed angle, since it depends on various factors, such as surface roughness, temperature, humidity, pressure, among others.

The angle of repose

For its part, the angle of repose is the maximum angle that an object can have when at rest on an inclined surface without falling. Unlike the angle of friction, the object is not in motion nor are there forces pushing it.

That is, if an object is placed on an inclined plane at an angle less than the angle of repose, it will remain stationary without sliding. On the other hand, if the angle exceeds the angle of repose, the object will begin to slide across the surface.

Important differences between both angles

• The angle of friction refers to the maximum angle of inclination that an object can have before starting to slide on a surface, while the angle of repose is the maximum angle that an object can have without starting to slide, even when at rest.
• For an object to begin to move, the angle of friction must be exceeded, while for an object to begin to slide while at rest, the angle of repose must be exceeded.
• The angle of friction varies depending on the friction force acting between the surface and the object, while the angle of repose does not vary since there are no forces acting on the object when it is at rest.

In short, both the angle of friction and the angle of repose refer to the maximum inclination that an object can withstand on an inclined surface. Both concepts are fundamental for the study of physics and mechanics, since they allow us to know the stability of an object in different situations.

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