What is Friction: Definition and 999 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.

View More On Wikipedia.org
Recent contents Top users
  1. SilverSoldier

    Mathematically Modeling a Rolling Body with Slipping

    Basically, I want to know if my assumptions and workings are correct. This is how I see this situation. First, I'm viewing this body as a series of disconnected points, like I have in this animation I made, modeling purely rolling motion. Modeling the body like that worked in that case, and...
  2. K

    Discovering Train Friction: Measuring Aerodynamics on Rails

    Summary:: How can I measure the friction of a train with its rails and the air. How can I measure the friction of a train with its rails and the air. You can assume that the face of the train is like the picture below. If you need any specifications just let me know
  3. M

    Problem with the friction model in an Abaqus simulation

    Hello, I have faced a weird problem and would really appreciate any comments. Assume a 2D model e.g. an axisymmetric model, meshed with quad, linear, and reduced integration elements. As you now if a model contains contact, we will get "CSHEAR1" and "CSHEAR2" in outputs. Assuming that the...
  4. M

    Thermodynamics Problem: Cylinder-Piston System with Friction

    Hi guys, First of all I'm sorry for my bad english I'll try to be as clear as possible. I have tried to solve this problem to understand the First Law of Thermodinamics: Q+L=ΔE_t In fact I know L (in the current convention) is the work which the envirorment does on the system but I don't...
  5. rakailee

    Box on a slanted plank with friction attached to a spring

    I first find the force of friction to be (2)(9.8)cos(65)(.22), then I find the pull of gravity to be (2)(9.8)sin(65). The full equation I set up to be: 0 = kx + force of friction minus the pull of gravity This gives me the wrong answer, 0.44 . My free-body diagram is that kx and force of...
  6. Haorong Wu

    Friction is electricmagnetic force; why friction is not conserved?

    Obviously, friction is not a result of other three kinds of force, and electricmagnetic force is conserved, then why friction is not conserved?
  7. studentgrade12

    Using a rope to pull a box across a floor (problem with friction)

    I have been trying a couple of problems with forces and i am not getting the answer, I don't understand what i am doing wrong. Can someone please guide me through this question
  8. SpaceThoughts

    Low friction horizontal rotating platform

    I am looking for a rotation devise like that one in this video below (from 00:40 seconds). Does anyone know where to get one, or have any idea about how to create a nice and stable rotation setup for experiments without too much hassle and DIY? A bike wheel won't do, a disk is better, because I...
  9. M

    A critically damped simple harmonic oscillator - Find Friction

    c = Critically Damped factor c = 2√(km) c = 2 × √(150 × .58) = 18.65 Friction force = -cv Velocity v = disp/time = .05/3.5 Friction force = - 18.65 * .05/3.5 = -.27 N I am not sure if above is correct. Please check and let me know how to do it.
  10. Leo Liu

    Is Kinetic Friction a Conservative Force?

    If a block slides down an inclined surface under the presence of the kinetic friction, does that mean the total energy lost by the block is equal to the work done by the kinetic friction? Thanks in advance.
  11. K

    Static friction — Experiment pulling different blocks across a surface

    I know that I am supposed to use the equation I wrote, but how do I find the maximum force of static friction and coeffcient of static friction if none of them are given beforehand? I can't have to unknowns in an equation. We then did the same thing, the only difference was then to measure the...
  12. MathDestructor

    Mechanics: Slope Friction Problem

    So far, I have this: For Part ii) I know that: mgh = xmgsin(theta), but I don't know how to go further
  13. kuruman

    Work is not done by static friction when accelerating a car

    A recent thread posed the question whether work is done by static friction in the case of an accelerating car. Before I had a chance to reply, the thread was closed on the grounds that the subject was "beaten to death". Undaunted, I am determined to deliver the coup de grâce here with a simple...
  14. Kaushik

    Why does an increase in surface area lead to a reduction in pressure?

    From what I read on the internet I found that increase in surface area that is in contact is offset by the reduction in pressure. What exactly does it mean? This is what I understood from the it (but my understanding might be absurd :-p): does reduction in pressure mean that the "hills" or...
  15. Helena Durrant

    Problem involving friction, with a mass being pulled up a slope

    (The answer from the markscheme is 26.7)
  16. A

    Is there any work done by static friction when accelerating a car?

    I'm asking for clarification, but it's my understanding, that of the thread below, and my college physics book Paul A tipler, that when walking or driving a car, the force of friction from the ground does no work. This makes sense in a car becuase the engine/fuel makes the power, driving the...
  17. F

    How does ultrasonic oscillation reduce sliding friction?

    Hi everyone! Sorry if I'm not able to work through this problem very much myself... I'm a Food Science student, and I'm trying to read an article about ultrasonic cutting when applied to apple slicing. From the papers they reference, the rapid vibrations on the blade reduce the friction...
  18. Thijske

    Kinetic friction coefficient of aluminum on lubricated cast iron

    Hey all, I was recently searching for kinetic friction coefficients, and I noticed that for a reason which is unknown to me, some materials had not been appointed such coefficient. The specific kinetic friction coefficient that I'm looking for is aluminum on greasy/lubricated cast iron. Any type...
  19. nilsvoorkamp1

    What Is the Coefficient of Kinetic Friction for Greasy Aluminum on Carbon?

    I need the coefficient of kinetic friction for movement between greasy aluminium on carbon. It's nowhere to be found on the internet. Thanks in advance!
  20. Thijske

    Calculate friction in an unusual manner.

    This is quite a specific case: I would like to calculate how much friction force is exerted between the rotating rod and the stationary circular thing. I guess we can't just use the formula of static/kinetic friction, because I don't think a normal force is of application... In the image, Fres>...
  21. T

    AP Physics 1 Help? Centripetal motion/Kinematics/Friction problem

    I think I have solved the first three, and only really need help on question four. For number one, I used Fc = (Mv^2)/R and just rearranged it for velocity so I ended up with v = sqrt(ac * R) For number 2 I used Ff = Fn*mu and got Mg*mu = Ff For number 3 I used w = Ff*d and got w = -Mg*mu*l...
  22. K

    B Resistive force that a nail will have to overcome to penetrate a piece of wood

    lets say a hammer of 0.5kg strikes a nail at 10m/s. The nail penetrates into the wood by 1cm. The reason why the nail stops is because friction has eventually overcome the nails momentum. The retardation of the nail can be worked out, but Can you calculate the force that stops the nail if you...
  23. R

    Working with Newton's Third Law and friction

    I know that the normal force and Fg are unbalanced in this case, but I don't get how to set up the equilibrium equations with that. I struggle with determining what you set the equations equal to when its either balanced or unbalanced forces you're dealing with.
  24. Petronius

    Newton's third law problem/kinematics (Airboat problem/no friction)

    Thank you very much your time! I first found the force of the air on the boat using the principle of Newton's third law and the fact that no friction is involved. Faction= -Freaction 150 N backwards = -150 N backwards 150 N backwards = 150 N forward I then sought to determine the...
  25. Prabs3257

    Velocity of an object on an inclined plane

    I used work energy theorem between initial top point and point x along the incline(downwards) i got the expression of v then diffrentiated it to get a maxima but it gives me a wrong ans which is 10/6 but the actual ans is 10/3 please tell me what i did wrong
  26. M

    Hydraulic pressure/flow -- friction loss question

    Flow delivered by a pipe can be calculated from input pressure, inlet geometry, pipe length, and a flow coefficient related to pipe cross-section, shape, and roughness. If we create an example of a pipe attached at the bottom of a self-refilling standpipe, which automatically supplies a...
  27. E

    Further Applications of Newton's Law : Friction, Drag, and Elasticity

    θ = 4 μs = 1 Fnet = Wpararell + fs m.a = 1/2.m.g.sinθ + μs.1/2.m.g.cosθ (divide by m) a = (g.sinθ+μs.g.cosθ)/2 a = ((9.8)sin4 + (1)(9.8)cos4)/2 a = 5.23 m/s^2 hello guys, I'm having trouble with this problem. Can anybody help me correct my attempt and explain it to me?? thanks
  28. Ranku

    I Dynamical friction in galaxies

    Analysis of dynamical friction in clusters of galaxies produces mass segregation between heavier matter at the center and light matter diffused in the outer regions (Ref). Can the flat rotation curve in an individual spiral galaxy, whereby heavier matter is concentrated at the center and...
  29. Huger

    Friction coefficient and the force on a syringe plunger

    I need to conduct an experiment and measure how what is the coefficient and force of friction of the rubber that pushes down along the edge inside the syringe. The thing is I can’t use a dynamometer.
  30. K

    Multi-surface Frictional force

  31. Isabel1747

    Rotational Inertia and Net Torque with Friction

    I converted the amount of rotations completed in 5 seconds into radians. 23.4 rot * 2pi = 147 rad I found the angular acceleration of the object in the first 5 seconds it was speeding up. Wf = Wi + at a = 5.881 rad/s^2 I then used the moment of inertia given in the problem to solve for torque. T...
  32. F

    Rolling friction and static friction....

    Hello, Static friction implies no relative (maybe just instantaneously) motion between the two objects that are in contact. Rolling friction pertains to rolling objects and develops due to the asymmetric deformation of the surface over which the body rolls (if the deformation was symmetric, the...
  33. 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...
  34. DavidOB18

    How Can a Stationary Top Block Accelerate with the Bottom Block?

    I know the answer but don't understand the concept. The solution says the accelerations are the same but if the top block is at rest how can it be accelerating. I know you can view both blocks as the same system but can you not study them independently. Any help would be appreciated.
  35. minadd

    Find all forces & the coeff. static friction of a pulley at equilibrium

    Given: (block a) m = .500kg (block b) m = .200kg that's all... Fg (block a) = (.5)(9.81) = 4.905N = Fn Fg (block b) = (.2)(9.81) = 1.962N i think acceleration might go like... a = (1.962)/(.5 + .2) = 2.8m/s^2 but isn't it supposed to be at equilibrium? So 0m/s^2. How am I supposed to find...
  36. Alfreds9

    Saw characteristics influencing efficiency in sawing steel?

    Hello, I am having a headache to try understand a possibly simple real-world problem: efficiency (as in number of strokes/cumulative length needed) to saw steel, assuming a constant sawing length per stroke and a known steel sectional area. I began to think about the few assumptions I assume...
  37. Kermit_the_Phrog

    Work in tightening a nut, given max torque and friction torque?

    NOTE: THIS IS THE GRAPH PROVIDED At first I approached this problem attempting to solve for the total work done, using the formula Wtotal = Wmaxforce - Wfriction I then subbed into the formula, representing the values of work as their torque value times theta, which gave me a longer algebraic...
  38. danielp3

    Calculating Torque for Rotating Wheels: Factors to Consider

    Say I have a motor connected to a wheel, the wheel is driven forward. The motor produces a certain torque rotate/turn the wheel right or left, how do I calculate the torque needed to rotate? keep in mind the friction between the surfaces, the mass of the wheel and the tire sag/subsidence due to...
  39. torito_verdejo

    Equations of motion in a free fall with friction

    I'm stack at the very beginning. If I use Newton's second law to find acceleration and integrate until I find the position, I must face $$v(t) = \int_0^t g-\frac{\lambda v}{m} dt'=gt-\frac{\lambda }{m} \int_0^t\frac{\partial z}{\partial t}dt$$ But this last term feels pretty weird. I don't...
  40. 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 |...
  41. brotherbobby

    How Does Braking Compare to Turning in Avoiding Collisions?

    1. For the car to apply brakes, we have ##v^2=2ar⇒a=\frac{v^2}{2r}=μg\;\;[ma=μmg]⇒v=\sqrt{2μgr} ## 2. For the car to go in a circle ##\frac{mv^2}{r}=μmg\Rightarrow v=\sqrt{\mu gr}##. We find from above that the maximum velocity ##v## possible to avoid a collision is ##\sqrt{2}## times as much...
  42. brotherbobby

    What is the maximum tension and friction force for a block held on an incline?

    (a) Ridiculously simple though it looks, I can't see how the string will be tight. One of the two has to be true. (1) The static friction ##f_S = mg \sin\theta = 25\times 10\times \sin 30^{\circ} = 122.5\; \text{N} ##. The maximum static friction ##f_S = \mu mg \cos \theta = 0.6\times 25\times...
  43. 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...
  44. Like Tony Stark

    Difference between static and kinetic friction

    I always read that the static friction applies when the object is not moving. If it starts moving then you have kinetic friction. But suppose the case of a block on conveyor belt. The block is moving, but I was told that that friction was static friction. Or suppose the Death Wall. I've also...
  45. S

    Static Friction in Circular Motion

    A) So we are given the radius and the coefficient of static friction as 3.0 m and 0.28 respectively. I know that in the vertical direction the only forces acting are the normal force and the gravitational force. Therefore, the normal force is equal to mg because net force is equal to 0, due to...
  46. A

    Work of a object moving across surfaces with different friction

    Homework Statement: Hetsut is the foreman of a construction project in ancient Egypt. He needs to move a giant block of stone, of mass 12 metric tons, from the docks to the temple grounds. He can go along the roads by traveling 295 meters east, then 89 meters north. Along the roads, the...
  47. brotherbobby

    External force on three blocks stacked

    The figure is shown above. In order to facilitate solution, I need to separate each block and draw the free-body diagram (FBD) with all the forces acting on it. 1. Let me start with the lowest block. Let me put its FBD as shown below. For forces in the vertical direction, ##N_3 = N_2 + m_3 g...
  48. Addez123

    Find the kinetic friction coefficient

    Image1, the exercise. My solution: Image2, my solution The answer is .37 but I keep getting .45 What am I doing wrong?
  49. S

    Using Newton's Laws: Friction, Circular Motion, Drag Forces

    Here is my attempt at setting up the equation: I set up the equation to find the acceleration of the box: F-Ffr= m*a after finding the acceleration, I can use the acceleration and plug it in the formula v^2=(v0)^2+2*a(x-x0), which will get me the value of (x-x0)The solution sheet says that F...
  50. Like Tony Stark

    Forces acting on a block which is lying on another block

    Well, I'm having trouble with the free body diagrams. For ##A## we have ##y)## weight, normal force, contact force with ##B##, ##F . sin(36.8°)##. And the acceleration is ##0## because we want to calculate the maximun force before moving. ##\Sigma \vec F = m . a_y## ##\vec N_A + \vec F ...
Back
Top