is a force that opposes motion between surfaces. It's crucial for everyday activities like walking and driving, but can also cause wear and tear on machines. Understanding helps us navigate the physical world and design efficient systems.
There are three main types of friction: static, kinetic, and rolling. Each type has unique characteristics and equations. By applying these concepts and using problem-solving techniques, we can analyze friction in various real-world scenarios and predict object behavior.
Friction
Principles and effects of friction
Friction opposes relative motion between two surfaces in contact acts parallel to surfaces opposite to direction of motion or attempted motion
Friction converts kinetic energy into thermal energy (heat) through surface interactions at microscopic level
Friction enables walking, running, driving without slipping by providing necessary traction between surfaces (shoes and ground, tires and road)
Friction causes wear and tear on moving parts in engines and machines leads to reduced efficiency and eventual failure
Friction generates heat beneficial for keeping hands warm but detrimental causing overheating of components (bearings, gears)
Friction can occur through (molecular bonding between surfaces) or (mechanical interlocking of surface irregularities)
Types of friction compared
(fs) prevents object from starting to move when force applied exists between two non-moving surfaces relative to each other
Examples: book resting on table, person standing on ground
Maximum force: fs,max=μs[N](https://www.fiveableKeyTerm:N), μs = coefficient of static friction, N =
(fk) opposes motion of object sliding over another surface exists between two moving surfaces relative to each other
Examples: sliding box on ramp, skier gliding down slope
force: fk=μkN, μk = coefficient of kinetic friction
(fr) opposes motion of rolling object exists when object rolls on surface without slipping generally smaller than static and kinetic friction
Examples: car tires on road, ball rolling on ground
Problem-solving with friction coefficients
Identify type of friction (static, kinetic, rolling) acting on object
Determine (N) acting on object typically equal to object's weight (mg) on horizontal surface
Use appropriate friction coefficient (μs, μk, μr) for given scenario
Apply Newton's second law (∑[F](https://www.fiveableKeyTerm:f)=ma) to set up equations involving friction and other forces
Objects at rest or constant velocity: ∑F=0
Objects accelerating: ∑F=ma, m = mass, a = acceleration
Solve equations to determine unknown forces or accelerations in problem
Analyzing friction in various scenarios
Free body diagrams: Visual representations of all forces acting on an object, including friction, normal force, and other relevant forces
Inclined planes: Friction analysis becomes more complex, as normal force is not equal to the object's weight
: Fundamental principles used to analyze friction problems and predict object behavior
Key Terms to Review (35)
Abrasion: Abrasion is the process of wearing or grinding away a surface through friction, often caused by the rubbing or scraping of one material against another. It is a key concept in the study of friction and its effects on physical systems.
AC current: AC current (Alternating Current) is an electric current that reverses its direction periodically. It is the form of electrical energy commonly delivered to businesses and residences.
Adhesion: Adhesion is the phenomenon where two different surfaces or materials are held together by intermolecular forces, without the involvement of any intervening liquid. It is a fundamental concept that underpins various physical and biological processes, from the ability of geckos to climb walls to the cohesion of liquids and the function of biological membranes.
Amontons: Amontons is a key concept in the study of friction, which is the force that opposes the relative motion between two surfaces in contact. Amontons' principles provide a fundamental understanding of the behavior and characteristics of friction, which is essential in various fields of physics and engineering.
Asperities: Asperities refer to the microscopic irregularities or protrusions on the surface of two contacting materials. These surface imperfections play a crucial role in the behavior of friction between the surfaces.
Coefficient of Friction: The coefficient of friction is a dimensionless quantity that describes the ratio of the frictional force between two surfaces to the normal force pressing them together. It is a fundamental parameter in the study of friction and plays a crucial role in understanding the behavior of objects in motion or at rest on various surfaces.
Coulomb: Coulomb is the fundamental unit of electric charge, named after the French physicist Charles-Augustin de Coulomb. It is a measure of the amount of electric charge and is a crucial concept in understanding various topics in electricity and magnetism, such as static electricity, electric fields, electric potential, and the behavior of charged particles.
Coulomb force: Coulomb force, also known as the electrostatic force, is the force of attraction or repulsion between two charged particles. It follows an inverse-square law and is governed by Coulomb's law.
Coulomb's Law of Friction: Coulomb's law of friction describes the relationship between the force of friction acting between two surfaces in contact and the normal force pressing them together. It states that the frictional force is proportional to the normal force and independent of the area of contact between the surfaces.
F: The symbol 'f' is used to represent various physical quantities in the fields of friction, Hooke's law, and oscillations. It serves as a variable or parameter that helps describe and quantify these important concepts in physics.
Fluid Friction: Fluid friction, also known as viscous drag, is the force that opposes the relative motion between a fluid, such as a liquid or gas, and a solid surface. This frictional force arises due to the viscosity of the fluid and the interactions between the fluid molecules and the surface of the object moving through the fluid.
Free Body Diagram: A free body diagram is a visual representation of the forces acting on an object or system. It is a fundamental tool used in physics to analyze the forces and their effects on the object's motion or equilibrium.
Friction: Friction is the resistive force that occurs when two surfaces interact, opposing the relative motion between them. It acts parallel to the surfaces in contact and can be either static or kinetic.
Friction: Friction is the force that opposes the relative motion between two surfaces in contact. It arises from the microscopic interactions between the surfaces and acts to resist their sliding motion, dissipating energy in the process.
Frictional Force (fk): Frictional force, denoted as fk, is the force that opposes the relative motion between two surfaces in contact. It arises due to the microscopic irregularities and interactions between the surfaces, and its magnitude depends on the characteristics of the surfaces and the normal force acting between them.
Fs: fs, or force of friction, is the force that opposes the relative motion between two surfaces in contact. It arises due to the microscopic irregularities on the surfaces and acts to resist the sliding or rolling of one surface over the other.
Inclined Plane: An inclined plane is a simple machine that consists of a flat surface tilted at an angle, used to raise or lower objects by applying a force parallel to the surface. It is one of the six classical simple machines and plays a crucial role in various physical phenomena and applications.
Kinetic friction: Kinetic friction is the force that opposes the relative motion between two surfaces in contact when they are moving past each other. It acts parallel to the surfaces and opposite to the direction of motion.
Kinetic Friction: Kinetic friction is the force that opposes the relative motion between two surfaces in contact. It arises when one surface slides over another and acts to resist the motion, dissipating energy in the process. Kinetic friction is an important concept in understanding Newton's First Law of Motion, problem-solving strategies, and the broader topic of friction.
Lubrication: Lubrication is the process of reducing friction between two surfaces in contact with each other by introducing a substance, known as a lubricant, between them. This helps to minimize wear, tear, and energy loss, improving the efficiency and lifespan of mechanical systems.
N: N is a variable or constant that represents a specific quantity or value, and it is commonly used in various scientific and mathematical contexts. This term is particularly relevant in the topics of Friction, Variation of Pressure with Depth in a Fluid, Hooke's Law: Stress and Strain Revisited, and Quantum Numbers and Rules, where it serves different purposes and carries distinct meanings.
Newton's Laws of Motion: Newton's Laws of Motion are a set of three fundamental principles that describe the relationship between an object and the forces acting upon it, governing the motion of objects and the interactions between them. These laws form the foundation of classical mechanics and are crucial in understanding various topics in introductory college physics.
Normal force: The normal force is the perpendicular contact force exerted by a surface on an object resting on it. It counteracts the weight of the object.
Normal Force: The normal force is a contact force that acts perpendicular to the surface of an object in response to an external force pressing the object against the surface. It is a fundamental concept in classical mechanics, particularly in the study of Newton's laws of motion.
Rolling Friction: Rolling friction is the force that opposes the motion of a rolling object, such as a wheel or a ball, as it moves along a surface. This type of friction is generally lower than sliding friction, as the rolling object experiences less resistance compared to an object that is sliding across a surface.
Static friction: Static friction is the force that resists the initiation of sliding motion between two surfaces in contact. It acts parallel to the surface and opposite to the direction of potential movement.
Static Friction: Static friction is the force that opposes the relative motion between two surfaces in contact with each other when they are at rest. It is the frictional force that must be overcome to initiate motion between the surfaces. This term is crucial in understanding concepts related to Newton's First Law of Motion, problem-solving strategies, the nature of friction, stability, and the applications of statics.
Stick-Slip: Stick-slip is a phenomenon that occurs in the context of friction, where an object initially remains stationary (sticking) due to static friction, but then suddenly slips or moves due to the buildup and release of kinetic energy. This cyclical pattern of sticking and slipping can lead to vibrations, noise, and other dynamic effects.
Surface Roughness: Surface roughness is a measure of the texture or irregularity of a surface, which can have significant impacts on various physical phenomena, including friction and the onset of turbulence. It is a fundamental concept in the fields of tribology and fluid dynamics.
Tribology: Tribology is the study of the principles of friction, lubrication, and wear between interacting surfaces in relative motion. It encompasses the design, friction, wear, and lubrication of interacting surfaces, with the goal of achieving efficient and effective performance of mechanical systems.
Tribometer: A tribometer is a device used to measure the coefficient of friction between two surfaces in contact. It plays a crucial role in understanding and quantifying the frictional forces that arise during the interaction of materials, which is a fundamental concept in the study of physics, particularly in the topic of friction.
μ: The Greek letter μ, or mu, is a commonly used symbol in physics that typically represents the coefficient of friction. The coefficient of friction is a dimensionless quantity that describes the ratio of the frictional force between two surfaces to the normal force pressing those surfaces together.
μk: μk, also known as the coefficient of kinetic friction, is a dimensionless quantity that represents the ratio of the force of kinetic friction between two surfaces in contact to the normal force acting between them. It is a crucial parameter in the study of friction and its effects on the motion of objects.
μr: The coefficient of friction (μr) is a dimensionless quantity that represents the ratio of the frictional force between two surfaces to the normal force acting between them. It is a fundamental parameter in the study of friction, which is a crucial concept in the field of physics, particularly in the topic of 5.1 Friction.
μs: The coefficient of static friction, denoted as μs, is a dimensionless number that represents the ratio of the maximum static friction force between two surfaces to the normal force pressing them together. This value indicates how much force is required to overcome the initial resistance to motion when an object is at rest. It plays a crucial role in understanding how objects interact at rest and helps predict whether an object will start moving under applied forces.