"Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other."
Deals with the force that opposes the motion of objects.
Definition of friction: The force that opposes the relative motion of two bodies in contact.
Types of friction: Static, kinetic, rolling, and sliding.
Coefficient of friction: A dimensionless constant that determines the magnitude of friction between two surfaces.
Laws of friction: Amontons’ laws, Coulomb’s laws, and laws of friction in rolling.
Factors affecting the coefficient of friction: The nature of surfaces in contact, force of contact, and the presence of lubricants.
Applications of friction: In brakes, in clutches, in bearings, in belts and pulleys, and in road safety.
Frictional losses: Energy losses due to friction in machines, such as heat generation.
Frictional force: Calculation and measurement of frictional force.
Friction and motion: Frictional force and its effect on motion, including acceleration, velocity, and displacement.
Static and kinetic friction: Differences between static and kinetic friction, and the relationship between the two.
Angle of friction: The angle between the normal reaction of a surface and the resultant force of friction acting on an object.
Limiting friction: The maximum possible force of friction before the object starts moving.
Friction and work: The relationship between friction and work, including work done against friction.
Friction in fluids: The effect of viscosity on fluid friction and its use in lubrication.
Laws of friction in fluids: Poiseuille’s law and Newton’s law of viscosity.
Tribology: The study of friction, wear, and lubrication between interacting surfaces, particularly in machines and engines.
Friction in nano-scale systems: Properties and effects of friction in nano-scale systems, including frictional forces at atomic and molecular levels.
Frictional properties of materials: Differences in the coefficient of friction between various materials.
Friction and wear testing: Methods used to test friction, wear, and lubrication of materials.
Applications of tribology: Usage of tribology in various fields of engineering, including aerospace, automotive, and medical devices.
Static friction: This is when two objects are in contact with each other, but there is no motion between them. Static friction is what keeps a book from sliding off a table when it is placed on it.
Kinetic friction: This is the friction that occurs when two objects are in motion relative to each other. This type of friction is the reason that it is more difficult to move a heavy object than a light one.
Rolling friction: This type of friction occurs when an object is rolling across a surface. It is the reason why it is easier to push a wheelbarrow than to drag it.
Fluid friction: Fluid friction occurs when an object moves through a liquid or gas. This type of friction is what makes it more difficult to swim through water than to walk on land.
"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."