What is Coefficient of friction: Definition and 416 Discussions

Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other. There are several types of friction:

Dry friction is a force that opposes the relative lateral motion of two solid surfaces in contact. Dry friction is subdivided into static friction ("stiction") between non-moving surfaces, and kinetic friction between moving surfaces. With the exception of atomic or molecular friction, dry friction generally arises from the interaction of surface features, known as asperities (see Figure 1).
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.When surfaces in contact move relative to each other, the friction between the two surfaces converts kinetic energy into thermal energy (that is, it converts work to heat). This property 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 component of the science of tribology.
Friction is desirable and important in supplying traction to facilitate motion on land. Most land vehicles rely on friction for acceleration, deceleration and changing direction. Sudden reductions in traction can cause loss of control and accidents.
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 impractical and necessitates the use of empirical methods for analysis and the development of theory.
Friction is a non-conservative force – work done against friction is path dependent. In the presence of friction, some kinetic energy is always transformed to thermal energy, so mechanical energy is not conserved.

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  1. I

    Investigation regarding the rotor ride

    So far some of the topics I can think of are Investigating how angular velocity affects the centripetal force experienced by riders on the rotor or the coefficient of friction required to pin the rider to the wall.
  2. A

    I If frictional force in system is <= us*N then there is no slipping

    If frictional force in system (say a block being pushed on a horizontal surface) is less than or equal to us*N then there is no slipping. Why is it that if the frictional force (Ff) in the system is greater than us*N then there is slipping (I am finding it hard to wrap my head around this)? us...
  3. C

    How to find coefficient of friction of a body sliding down the slope?

    So basically I need to find the coefficient of friction given the listed information. What bothers me is that I am getting two different accelerations for two different approaches. When I calculate acceleration using Fg=mgsin60 I do it this way: Fg=mgsin60 -> ma=mgsin60 ->a=gsin60 -> a=8.66. But...
  4. Daniel Guh

    Mechanical Physics: Coefficient of Friction

    First of all, the pulling force is 300N cos(30) = 260 N At this point, I try to find the friction force Fn = mg = 20kg * 9.81 m/s^2 = 196.2 N Then, Ff = μ * Fn = 0.5 * 196.2 N = 98.1 N So after canceling the horizontal forces, 260N - 98.1N = 161.9N And the acceleration will be 161.9N / 20kg =...
  5. Arwing

    Can't remember equation for coefficient

    We did a lab in class on how to calculate it but he collected it and its days later, can't remember how to attempt it.
  6. Fatboyx

    I Pulling cable through underground ductwork.

    Hello all, I am an Engineering dropout turned Cable Splicer. In my job we do a lot of Heavy Duty underground cable pulling. Usually plastic jacketed cable through some type of ductwork (typically plastic as well). We use a winch truck and a heavy rope to pull this cable through the ducts...
  7. rudransh verma

    Coefficient of friction and normal force

    The answer should be no change but we know ##F=ma##. In this eqn when acceleration increases mass decreases for same force. So why not here? If normal is doubled ##\mu## should be halved.
  8. Send-Help

    Find tangential velocity given radius and the coefficient of friction

    I have attempted to solve for the velocity by setting the centripetal force (mv2)/r to the normal force pointed to the center of rotation (mg). This approach seems to give the incorrect solution and I am unsure of my misunderstandings.
  9. ineedhelpthanks

    Inclined plane problem without mass or coefficient of friction given

    Confused how to approach problem after making a free body diagram and finding the length of the inclined plane
  10. GiriBang

    What happens when the coefficient of friction is 0?

    My physics teacher said something shocking a few months ago. During a lecture, he asked what would happen if mu of a solid is zero? We answered that the solid will slide very smoothly but he said the Electrostatic attraction would make it hard to slide as the distance between the two surfaces...
  11. Cheesycheese213

    Measuring the coefficient of friction

    Hi! Sorry if this isn't a good question, but for an experiment, I wanted to try measuring the coefficient of friction of frozen solutions, but wasn't sure how to do it? I thought that since ice would have a low coefficient of friction, it would be interesting to see if solutions with water and...
  12. trASHf

    How to find the coefficient of friction?

    GR (bold = mathematical convention) m = 3.2kg |applied force| = + 22.8 N |acceleration| = + 3.02 m/s^2 FBD-hypothetical ^ normal force | friction force <-----*-----------> applied force |...
  13. cs44167

    What is the coefficient of friction for a pen rolling down a book?

    I tried using coefficient of friction = friction / Normal force, but needed a value for friction. I then tried to find the friction using a = f/m, but was unsure of which value to plug in for force. Simply finding the force given a and m will not yield the correct answer; the net force must be a...
  14. H

    Calculating the coefficient of friction Given 2 forces and and angle

    i tryed putting all the number into that equation but it does not work, i have no clue if i need to include the angle to solve this or not and if i do i have no clue how i would
  15. Manasan3010

    Kinetic coefficient of friction greater than the static coefficient?

    Are there any instances where kinetic coefficient of friction greater than static coefficient of friction? Is this possible in nature?
  16. W

    Find the force of Friction and minimum coefficient of friction

    Fg = mg = 50 * 10 = 500 N Fn = mg-ma = 500 - (50.0)(1.0) = 500-50 = 450 I don't necessarily know if this is right and I can't seem to find the Ff or coefficient of friction either. Please Help!
  17. Y

    [] An Experiment to Determine the Coefficient of Friction

    Homework Statement So in physics we have this lab. Its simple, I'm just bad at physics...so bare with me. The objective of the lab is find the coefficient of friction (on a flat surface not on inclined planes and such not sure if this makes a difference (I should know if it does but I don't and...
  18. A

    Finding Force by using the coefficient of friction and mass

    Homework Statement A man pushes a 50 kg box up a 20-degree ramp at constant velocity. If the pushing force is parallel to the ramp, and the coefficient of friction is 0.4, how much force is he pushing with? Homework Equations u=Fs, max/Fn Not sure if this equation is needed. The Attempt at a...
  19. S

    Dependence of friction on area.

    Hello Guys, I have been pondering on the nature of the frictional force and its dependency on the area of contact for the past few days and I had already searched for plausible explanations for the same.Although I could gather a few discrete points ,I couldn't get a complete picture of it. Some...
  20. U

    Question Concerning The Coefficient of Friction: Block on a Rough Inclined Plane

    Homework Statement A block of mass 20kg is on rest on a rough plane inclined at 60 degrees to the horizontal. A force P is applied to the block to "maintain equilibrium". P is parallel to the line of greatest slope of the inclined plane. The maximum value of P is twice the minimum value of P...
  21. Pedgepoke

    Ladder Leaning against wall -- find the coefficient of friction

    Homework Statement Ladder leans against wall at angle θ. It is L meters long and mass m. Find the coefficient of friction with the floor. Assume no friction at the top.[/B]Homework Equations ΣFx = 0 ΣFy = 0 Στ = 0 ƒ = μFn (Fn being the normal force with the ground) The Attempt at a Solution...
  22. physicsquestionboi

    Kinetic Friction Homework Help

    A steel washer is suspended inside an empty crate from a light string attached to the top of the crate. The crate slides down a long ramp that is inclined at an angle of 37 above the horizontal. The crate has mass 154 kg. You are sitting inside the crate; your mass is 61 kg. As the crate is...
  23. Liam C

    Coefficient of Friction when Normal Force is Reduced [HS]

    Homework Statement A 5.0kg block of wood sits on a table with a string running over a pulley suspending a mass. The largest mass that can be suspended without moving the block of wood is 0.75kg. a) Calculate the coefficient of friction in this case. b) What type of coefficient of friction has...
  24. P

    Calculate the coefficient of friction from mass and angle

    Homework Statement Determine the coefficient of friction for a surface when the mass of an object is 300g and the angle of incline when the object starts to move is 29° Distance traveled and acceleration are not provided Homework Equations W = mg Ffric = μN N = mg cos(θ) μN = mg sin(θ) The...
  25. A

    Coefficient of friction of a tire: with/without tread and wet/dry

    I'm new to the forum and after some help if anyone can explain. I've read a few articles now, which have stated that the average co-efficient of friction for a tire with tread will be between 0.4 in the wet and 0.7 in the dry. If instead the tire had no tread, the co-efficient of friction will...
  26. Y

    Coefficient of Friction With only Time and Distance

    Im a high school student and am in AP Physics 1. I just created a formula for calculating the coefficient of kinetic/static friction between two objects using only distance and time (I don't have a way to measure Newtons). Is it correct and can it be used in the real world?
  27. S

    How do i find the coefficient of static friction?

    Homework Statement A coffee cup in your dashboard slides forward when you decelerate from 20 m/s to rest in 3.5 s or less, but now if you decelerate for a longer time. What is the coefficient of static friction between your coffee cup and your dashboard? Homework Equations a = delta a / delta...
  28. Motzu2098

    Find the Coefficient of friction on a banked curve.

    Homework Statement A car giving a turn on a curve with 88m of radius, traveling at a speed of 95km/h, the curve is perfectly banked for a car traveling at 75 km/h, meaning that the curve has an angle θ of 26.7º. Homework Equations μ = ? r = 88m v = 26.38 m/s θ = 26.7º Ff = μ · g · m Fc = m...
  29. APphysicsSenior

    Acceleration of object with friction: Homework help

    A 50 kg box rests on the floor. The coefficients of static and kinetic friction are 0.70 and 0.50, respectively. a.) What is the minimum force required to start the box sliding from rest? b.) After the box starts sliding, the person continues to maintain that force. What is the...
  30. APphysicsSenior

    How to find coefficient of friction *Without* mass?

    A car traveling at 97 km/h can stop in 48 m on a level road a.) Determine the acceleration of the car b.) Determine the coefficient of friction between the tires and the road Homework Equations : Vf^2=Vo^2 +2aΔx μ=Ff/mg[/B] 3. I have part A, I got -7.53 m/s^2, but I can't seem to...
  31. A

    How is the minimum work needed to push a car up an inclined plane calculated?

    Homework Statement What is the minimum work needed to push a 1000-kg car 300 m up a 17.5 degree incline? A. Ignore friction B. Assume the coefficient of friction is 0.25 Homework Equations W = F*d Net force = ma The Attempt at a Solution At first I did: Work = F*300*cos17.6 but I later...
  32. L

    Help finding obscure coefficient of friction

    Homework Statement I have a homework assignment that requires me to use the coefficient of static and kinetic friction for rubber on wood. I cannot locate this value anywhere so far. Homework Equations None. The Attempt at a Solution I have searched and searched and I cannot find the...
  33. N

    Coefficient of friction in regards to a clamp force

    Does coefficient of friction change in regard to clamp force applied to parts? If you imagine a bench vice, clamping a plate with a weight attached. Can the clamp force required be calculated to hold a specific weight? I'm asking because I have an excavator mounted hammer EMV outside. It...
  34. Alexanddros81

    Banked Curve-Determine smallest static coefficient of friction

    Homework Statement 13.49 The flatbed railway car travels at the constant speed of 80 km/h around a curve of radius 55m and the bank angle 15deg. Determine the smallest static coefficient of friction between the crate and the car that would prevent the crate of mass M from sliding. Homework...
  35. D

    Coefficient of friction between stick and circle

    Homework Statement Using the results from problem 2.18 for the setup shown in the Figure below show that if the system is to remain at rest, then the coefficient of friction:a) between the stick and the ground must satisfy $$ μ ≥ \frac {sin(Θ)cos(Θ)} {(1+cos(Θ))(2-cos(Θ))} $$ Homework...
  36. J

    Minimum value of coefficient of friction

    Homework Statement Ans: c) Homework EquationsThe Attempt at a Solution I can solve this problem if only I understand the setup . I am sure the diagram is missing something . Can someone help me understand the problem statement in context of the setup ?
  37. EEristavi

    Automotive Friction force, Coefficient of friction &Traction

    I have few (more or less) general questions: 1. I know that: "The coefficients of friction are nearly independent of the area of contact between the surfaces". I understand this, but I know from everyday life, when car tire tread is worn off, braking distance increases and maximum acceleration...
  38. A

    Coefficient of friction between puck and ice

    Homework Statement [/B] A hockey puck travels across the ice at 6.5m/s. the puck travels a total of 7.6m. What is the coefficient of friction between the puck and the ice. Homework Equations [/B] fnet=ma Ffr= coefficient of friction x force normal The Attempt at a Solution [/B] I found my...
  39. R

    Coefficient of friction of various materials not listed in standard references

    I'm interested in finding out what the coefficient of friction would be for a few different materials such as:Copper on aluminum Copper on graphite graphite on aluminum I'm not sure if it matters if the order is reversed such as Aluminum on copper vs copper on aluminum.. also I've seen that...
  40. Abhishek Gupte

    Find the kinetic coefficient of friction (mu)

    Homework Statement A 1.0x10^3 kg elevator carries a maximum load of 800kg Velocity = 3m/s Distance = .01km Net work = 13640J Homework Equations Force of friction = (m)(mu)(gravity) The Attempt at a Solution Gravity = friction 9.8 = (mu)(17640) .001 = mu
  41. Harsh Patel

    How to find the Coefficient of friction from Fn and Ff Graph

    Homework Statement I have a Force Normal vs Force Friction Graph and I wan to find the coefficient of friction from the graph. Homework Equations The Attempt at a Solution I have tried the formula ff= uFN but my teacher is looking for me to do it using the graph
  42. Kinetic95

    Static coefficient of friction decreasing with normal force?

    In my experiments, on a flat plane, when I incrementally increase the normal force acting on a rubber block, I am measuring a decrease in the static coefficient of friction. I am also measuring the friction force, which increases as normal force increases BUT this is not a proportional increase...
  43. B

    Does Coefficient of Friction Change with Rougher Surfaces?

    Let's say you two objects with weight of 2 kilograms but one is narrower and one wider. They are said to be similar coefficient of friction against a surface.. but what if the surface is rough? Won't the wider object has more friction? Or still the same? If still the same.. what if the...
  44. I

    Which materials have the highest coefficients of friction?

    I am aware that there needs to be two materials for there to be a coefficient of friction, but I mean in general. For example, I know synthetic setae are very resistant to slipping on surfaces.
  45. F

    Maximum coefficient of friction

    This issue was the subject of this old post, now closed. The question is: can a coefficient of friction (static) be larger than one? I see confusing replies. Someone talks about glue, but I'm not convinced about that. It's a bit like wondering about the coefficient of friction of a wooden plank...
  46. HarshK

    Finding the coefficient of friction

    Homework Statement I am investigating a scenario where a pendulum with a bob attached is released from an angle and pushes a box to a certain distance. My goal is to find the coefficient of friction between the box and the surface it moved on. I have measurements for: - mass of the bob (125...
  47. K

    Find the velocity given coefficient of friction and radius?

    Homework Statement An disk has a radius of 0.2 meters. A lump of putty with a coefficient of static friction of 0.9 is stuck on the edge of the disk. Let's say the disk starts at rest and gradually speeds up. At what speed will the putty just barely be able to stay in place on the edge of the...
  48. T

    How to find Torque without Coefficient of Friction?

    Hello! I am an AP Physics student and had a quick question for validity. I was prompted with this question in class today: Example 7: An 8-meter ladder of weight 355 N leans at an angle of 50° to the floor against a smooth vertical wall. Assume the center of weight (gravity) for the ladder is at...