"Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other."
The force that opposes motion between two surfaces that are in contact. It is a major factor in many dynamics problems.
Force: A fundamental concept of physics, which is the push or pull on an object that causes it to move, accelerate or change its shape.
Newton's Laws of Motion: Three laws that describe the relationships between force, mass, acceleration, and motion.
Static Friction: The force that resists motion when two stationary surfaces are in contact with each other.
Kinetic Friction: The force that opposes motion when two surfaces are in relative motion.
Coefficient of Friction: A dimensionless value that represents the relationship between the frictional force and the normal force between two surfaces.
Frictional Force: The force that opposes the motion of an object when in contact with a surface.
Sliding Friction: A type of kinetic friction that occurs when two surfaces are sliding against each other.
Rolling Friction: A type of kinetic friction that occurs when a round object rolls over a surface.
Fluid Friction: A type of kinetic friction that occurs in fluids (gasses or liquids).
Shear Force: The force applied parallel to a surface, which causes deformation of the material.
Contact Area: The area of contact between two surfaces that affects the frictional force.
Lubrication: The use of a substance to reduce friction between surfaces in contact.
Wear: The gradual removal of material due to friction and/or erosion.
Traction: The maximum amount of force that can be transmitted between two surfaces.
Coulomb's Law of Friction: A simple model for the relationship between frictional force and normal force.
Limiting Friction: The maximum force of friction that can be applied before the object begins to move.
Angle of Friction: The angle between the normal force and the maximum force of friction.
Adhesion: The force that holds two surfaces together due to intermolecular attractions.
Cohesion: The force that holds two particles of the same substance together.
Hertz's Law: The relationship between the contact force and deformation for elastic solids.
Static friction: The frictional force that resists the relative motion between two stationary surfaces in contact.
Sliding friction: This type of friction resists the relative motion between two surfaces sliding over each other.
Rolling friction: Applies to the motion of rolling objects like wheels or balls, where the frictional force opposes the motion and affects its speed.
Fluid friction: Also known as air resistance, it is a type of resistance force that opposes the motion of objects through fluids like air or water.
Lubricated friction: In this type of friction, a lubricating substance like oil or grease is placed between two surfaces in contact, reducing friction.
Limiting friction: The maximum amount of force that can be applied to an object before it slips or starts to move.
Kinetic friction: A force acting between two objects moving relative to each other.
Dynamic friction: This is another name for kinetic friction or sliding friction.
Viscous friction: Resistance to relative motion within a fluid.
Coulomb friction: Also called dry friction, this is the friction between two bodies in contact without any lubrication.
Internal friction: The resistance between molecules within an object.
Skin friction: Resistance to the motion of a fluid against the surface of an object.
Tractional friction: This type of friction is the resistance of a surface to the slip of an object over it.
"Dry friction is subdivided into static friction ("stiction") between non-moving surfaces, and kinetic friction between moving surfaces."
"Dry friction generally arises from the interaction of surface features, known as asperities."
"Fluid friction describes the friction between layers of a viscous fluid that are moving relative to each other."
"Lubricated friction is a case of fluid friction where a lubricant fluid separates two solid surfaces."
"Skin friction is a component of drag, the force resisting the motion of a fluid across the surface of a body."
"Internal friction is the force resisting motion between the elements making up a solid material while it undergoes deformation."
"Friction can have dramatic consequences, as illustrated by the use of friction created by rubbing pieces of wood together to start a fire. Kinetic energy is converted to thermal energy whenever motion with friction occurs, for example when a viscous fluid is stirred. Another important consequence of many types of friction can be wear, which may lead to performance degradation or damage to components."
"Friction is a non-conservative force."
"In the presence of friction, some kinetic energy is always transformed to thermal energy, so mechanical energy is not conserved."
"Friction is not itself a fundamental force."
"Dry friction arises from a combination of inter-surface adhesion, surface roughness, surface deformation, and surface contamination."
"The complexity of these interactions makes the calculation of friction from first principles difficult."
"It is often easier to use empirical methods for analysis and the development of theory."
"Dry friction is subdivided into static friction ("stiction") between non-moving surfaces, and kinetic friction between moving surfaces."
"Another important consequence of many types of friction can be wear, which may lead to performance degradation or damage to components."
"Skin friction is a component of drag, the force resisting the motion of a fluid across the surface of a body."
"Fluid friction describes the friction between layers of a viscous fluid that are moving relative to each other, while dry friction is a force that opposes the relative lateral motion of two solid surfaces in contact."
"Kinetic energy is converted to thermal energy whenever motion with friction occurs, for example when a viscous fluid is stirred."
"Friction can have dramatic consequences [...] which may lead to performance degradation or damage to components."