Definitions [3]
Definition: Angle of Friction
The angle between the resultant force (combination of normal force and frictional force) and the normal force itself, related to the coefficient of friction as tan(ϕ) = μ, i.e., ϕ = tan−1(μ), is called the Angle of Friction.
Definition: Angle of Repose
The minimum angle of the rough inclined plane for which a body placed on it may just start sliding down, which is numerically equal to the angle of friction, is called the Angle of Repose.
Definition: Friction
The force which prevents or tries to prevent the slipping or sliding of two surfaces in contact, which can be high for dry and rough surfaces and low for smooth and wet surfaces, is called Friction.
Theorems and Laws [1]
Law: Laws of Friction
- First Law: When two bodies are in contact with each other, the direction of the force of friction on one at its point of contact is opposite to the direction in which the point of contact tends to move relative to the other.
- Second Law: When bodies are in equilibrium, the force of friction prevents the motion, which can be determined by using conditions of equilibrium of forces that act on the body.
- Third Law: The ratio of limiting friction to the normal reaction of surfaces depends on the nature of the substances and does not depend on the magnitude of the normal reaction.
- Fourth Law: The amount of limiting friction is independent of the area of contact or the shape of surfaces, provided the normal reaction remains unchanged.
- Fifth Law: During motion, the direction of friction is opposite to that of relative motion and is independent of velocity.
