What is Static friction: Definition and 505 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. O

    Mass is independent of tendency to break static friction?

    Hello, I'm trying to reconcile what seems to me to be a contradiction. Last week, I did a lab experiment where we stacked some metal bars in a tray and measured the force required to pull the tray into motion and break away from the force of static friction. As we predicted, the more mass we...
  2. N

    Static friction in two block problems

    Doubt - Force cannlt exceed limiting friction for a block to remain at rest on ground. However for to blocks to move together, it becomes more than limiting friction, yet only static friction is acting on the blocks? Which moves the lower block. How can it be more in this case? Relative...
  3. G

    Static friction between 2 blocks and tension of string

    Homework Statement the maximum force is F=F1 +F2 + T as shown in the textbook... I can't understand why the tension of spring is also = F1...Is it because of the writer assume the spring is directly attached to the part P (upper part of the block) ?? Homework EquationsThe Attempt at a Solution
  4. D

    Inclined plane static friction

    Homework Statement An ideal cord is connected to a wall on the top of an inclined plane at one end and is wound around a thin homogeneous cylinder of mass M and radius R. The inclination angle is ϑ and the static and dynamic friction coefficients between cylinder and plane are μs, μd , and the...
  5. TyroneTheDino

    Conceptual Question about Static Friction

    Homework Statement Today we were studying a block on an incline and determining the angle needed for the block to start sliding. The question asked is: Why is the equation for the coefficient of static friction independent of the weight of the block? Homework Equations ΣFx=Fapplied-fs=0...
  6. S

    Calculate force of friction on car as it rolls across

    Homework Statement Calculate the force of friction on a toy car as it rolls across a flat floor. Given: mass = 0.293kg time = 3.66 s displacement = 8.7Homework Equations Fnet = mass x acceleration displacement = [(velocity1 + velocity2)/2] time velocity2 = velocity1 + acceleration(time)The...
  7. T

    Why static friction not kinetic in this problem?

    Homework Statement The sports car ) is rounding a flat, unbanked curve with radius R . If the coefficient of static friction between tires and road is Us, what is the maximum speedat which the driver can take the curve without sliding? why in this problem i am given Static fiction coefficient...
  8. B

    Find force required to move pole with static friction

    Homework Statement The uniform 14-ft pole weighs 150 lbs and is supported as shown. Calculate the force P required to move the pole if the coefficient of static friction for each contact location is 0.40. (Sorry for the sideways images!) [/B] Homework Equations 1.) Fmax = μs*N 2.) ∑M = 0...
  9. *.*.*AnUm*.*.*

    Help in Homework -- difference b/w kinematics friction and static friction?

    Hi, Please explain what is the difference b/w kinematics friction and static friction ? Please explain, what is rolling friction ? Is it when we are pulling a weight with rope, and rope is rolling on a wheel ? for example in past days, people used rope to get water from well. Please explain...
  10. AlephNumbers

    Does Rolling Necessitate Static Friction?

    If smooth rolling motion does not necessitate static friction, which I have been led to believe by a certain @haruspex , then what other forces or principles could prevent a smoothly rolling body from slipping?
  11. N

    Finding the force to break static friction

    Homework Statement Samantha and Rebekah each push on a stack of doughnuts equally. If the coefficient of static friction is .28 and the box has a mass of 18kg, what force does each push individually to break static friction? Once it's moving, the coefficient of kinetic friction is .17, how much...
  12. B

    Finding the coefficient of static friction on an inclined pl

    Homework Statement So, I need to figure out the coefficient of static friction using the equation tanθ = µs ONLY. I have been given the angle 26 degrees, and a mass of 424.32g. Homework Equations tanθ = µs[/B] The Attempt at a Solution I don't know where to start...
  13. L

    Limiting friction Vs static friction

    Hello, members. What are static, limiting, kinetic, rolling frictions and sliding frictions? I'm unable to grasp what exactly the difference is. Could somebody give me an example that covers all of them (or some other example that could easily tell me the difference) so that it can be easy for...
  14. G

    Finding the static friction force

    Homework Statement A 60-kg person rides down an icy hill of 20° slope while standing on a 3.0-kg flat-bottomed bathroom scale. Assume there is no frictional force between the bottom of the scale and the hill. The static friction force the scale exerts on the person is Homework EquationsThe...
  15. goonking

    Static Friction of sliding box on plane

    Homework Statement Homework Equations Fs = μ FN The Attempt at a Solution Ok, so I drew a free body diagram and tilted it 90 degrees so that Fg of the small box points right and Fstatic points left. Fg = 4.7 kg x 9.8m/s2 = 46 N we want Fs to equal 46 N , correct? so we use the formula Fs...
  16. goonking

    Static friction and acceleration

    Homework Statement A glass of orange juice is on the floor of a subway car traveling along a straight path at constant velocity. The coefficient of static friction between the glass and the floor is 0.32. The subway suddenly accelerates forward. What is the maximum acceleration that the subway...
  17. akashpandey

    Why static friction is directely proposnal to normalreaction

    I want to know why Static friction∝normal reaction and Why not Static friction∝ area of surface Static friction∝weight
  18. B

    Calculating Coefficient of Static Friction on an Incline

    Homework Statement A 2 kg block rests on an inclined plane with an angle of 30. A force of 5 N is applied to the block in a direction down the incline plane until the block begins to move when the force reaches 7.3 N, what is the approximate coefficient of static friction between the block and...
  19. K

    Static friction between a cylinder and a wall

    Homework Statement The cylinder in the drawing weighs 100[N]. there is a horizontal rope at the top that prevents it from rolling. what is the coefficient of friction if it's on the verge of movement Homework Equations Friction force: f=μN The Attempt at a Solution The whole weight of the...
  20. H

    Calculating Coefficient of Static Friction to Keep Glider from Springing Back Left

    An air-track glider of mass 0.100 kg is attached to the end of a horizontal air track by a spring with force constant 20.0 N m (Fig. 6.22a). Initially the spring is unstretched and the glider is moving at 1.50 m s to the right. It is calculated that with an air air track turned off, a glider...
  21. Poetria

    Static friction and maximum/minimum force

    Homework Statement A block of mass m is at rest on an inclined plane of angle θ with respect to the horizontal. There is friction between the block and the inclined surface (μk and μs). Now, assume that the value of θ is less than the value in part A) (so that the block will remain stationary...
  22. L

    Static friction for a ball rolling without slipping

    Homework Statement A bowling ball rolls without slipping up a ramp that slopes upward at an angle β to the horizontal. Treat the ball as a uniform solid sphere, ignoring the finger holes. Explain why the friction force must be directed uphill. Homework Equations F=ma, torque=I(alpha)...
  23. I

    Finding horizontal force using mass and static friction?

    Homework Statement There is a box that has a mass of 30 kg. The coefficient of the static friction is 0.75. Find the horizontal force. Homework Equations Fs=muFn F=ma The Attempt at a Solution Fs=(.75)(.98)(.30)=.2205 N That is probably way off... I am very confused right now. Could someone...
  24. T

    Direction of static friction in rolling motion?

    I don't really have a specific problem, but for example, I was doing a problem where a constant force unwounds a spool of wire (a disk). The force pulls at the top of the disk to the right and the force of static friction is also at the bottom to the right, the same direction as the sphere is...
  25. A

    Coefficient of static friction

    I have to make 2 ramps of 30 cm long along with 2 objects(objects need to be 8 cm long). One must be slippery so that it has a low coefficient of friction and one needs to be sticky and have the highest coeffivient of friciton possible. Bassically we place object on ramp raise it from one side...
  26. 9

    Static Friction -- A ladder leaning against a wall starts to slip

    Homework Statement A ladder,10 m long and having a mass of 25 kg, rests on a rough horizontal floor and is supported by a rough vertical wall. The ladder is inclined at 60 degrees as shown and starts to slip when a person having a mass of 75 kg has climbed halfway up it. The coefficient of...
  27. S

    Coefficient of static friction problem

    Homework Statement I got this problem: A wedge of mass m = 36.1 kg is held in place on a fixed plane that is inclined by an angle θ = 21.3° with respect to the horizontal. A force F = 302.3 N in the horizontal direction pushes on the wedge, as shown in Figure 4.25a. The coefficient of kinetic...
  28. J

    Static Friction of a Car's Tyre

    Homework Statement I'm trying to understand how static friction opposes the motion of a moving car. From what I have read, the car tyre doesn't move relative to the ground. The car tyre pushes on the ground and the ground pushes back - this is how the car moves. The force of friction is in the...
  29. P

    Coefficient of static friction experiment

    [b]1. Problem I am currently doing a home experiment about the coefficient of static friction. I've set up a ramp and am testing at which angle a tissue box begins to movie (with five different masses in it)... Although for every mass I use the angle seems to remain the same. The angle at...
  30. H

    The wording "just begin to move" for the force of static friction?

    I am confused with the wording for a static friction problem; this particular wording also lead me to a conceptual question on the force of static friction. It all started with a question in my textbook that I figured out how to solve for the right answer. The question states, a box of m is...
  31. S

    Need some help finding applied force & coefficient of static friction

    i am having some trouble figuring this out I can not figure out which formula to use i have tried Mass x G x Static Friction which resulted in 1 x 2 x 9.8 = 19.6
  32. J

    Static Friction Experiment: Help Result interpretation

    Hello, I hope someone can help me with this question. "Design a simple experiment that you could carry out in your home to i) determine the coefficient of static friction between an object and a surface. ii) prove that the coefficient of static friction is dependent only on the surfaces in...
  33. J

    Coefficient of static friction of a sliding block

    Homework Statement block is placed on a ramp at an angle of 39.4 and height of the ramp is 1.610m and the mass of the block is 8.54kg if coefficient of kinetic friction is 0.111 and the coefficient of static friction is 0.173 what is the speed of the block at the bottom of the ramp. if it...
  34. R

    Inertia and static friction confusion

    In a recent physics class I took, my teacher explained how friction is not affected by surface area, but by the "bumpiness" of the two objects and the mass, as well as other things, but not the surface area. But this made me wonder how nails get harder to pull out the deeper they are embedded in...
  35. N

    Static friction does no work (energy is conserved)

    I have read that static friction does no work and energy of the system is conserved if only this type of friction exists. Is this only an experimental fact, or can it be proved from basic principles? If it can, how?
  36. C

    How does static friction do work?

    Homework Statement Static friction can never do work on an object. a. True b. False Homework Equations The answer is False, indicating that static friction can do work. The Attempt at a Solution W=fd, when d=0 w=0 regardless of the force. How does this work? Or is the online...
  37. D

    Coefficient of static friction of a sliding box

    Homework Statement A box rest on an incline making a 34 angle with the horizontal. It is found that a parallel force to the incline of at least 235 N can prevent the box from sliding down the incline. If the weight of the box is 800 N, find the coefficient of static friction between the...
  38. A

    How to Calculate the Required Force to Move a Block Up an Incline

    Homework Statement 4.00-kg block rests on a 30.0° incline as shown in the figure. If the coefficient of static friction between the block and the incline is 0.700, what magnitude horizontal force F must act on the block to start it moving up the incline? Homework Equations F=ma...
  39. T

    Use Work (net) to find coefficient of static friction and speed

    1. a 5.0 kg block is pushed up a wall by a 90N force. Assume that the block starts from rest and that it has an acceleration of 0.5m/s^2. a. find the coefficient of kinetic friction between the block and the wall. b. Find the work done by each force acting on the block. c. Find the...
  40. P

    Phys Static Friction Ramp Problem

    Homework Statement The problem reads : You are riding your motorcycle one day down a wet street that slopes downward at an angle of 20 ∘ below the horizontal. As you start to ride down the hill, you notice a construction crew has dug a deep hole in the street at the bottom of the hill. A...
  41. I

    Static friction of masses connected by a rod

    This isn't homework...I'm reviewing physics after many years of neglect. Given 2 masses, m_1, m_2, connected by a rigid, massless rod, stationary with respect to a ramp which makes an angle of \theta with the horizontal, with coefficients of static friction between the masses and the ramp =...
  42. A

    How Does Static Friction Maintain Equilibrium in a System of Balls?

    Homework Statement Two small balls, each of weight Wo, are supporting a big ball of weight W1, as shown in Figure Q2. The line connecting the center of the upper ball and that of a lower ball forms an angle of 45° with respect to the horizontal, as shown in Figure Q2. A block of weight Wo is...
  43. M

    Minimum coefficient of static friction problem

    Homework Statement I know the diameter is 30 m and the radius is 15 The period for one revolution I suppose is some multiple of 7.03 Homework Equations The Attempt at a Solution I couldn't think of an equation where friction was involved where rotational motion was concerned. I...
  44. N

    Circular Motion with static friction

    1. Homework Statement A bus passenger has her laptop sitting on the flat seat beside her as the bus, traveling at 10.0 m/s, goes around a turn with a radius of 25.0 m. What minimum coefficient of static friction is necessary to keep the laptop from sliding? Given: V = 10 m/s r = 25.0...
  45. J

    Static friction between two stacked blocks a 3rd law pair?

    I'm trying to get my head around this scenario: The blocks are at rest, despite the tension forces acting on them. It is obvious that the static friction acting on A from B is 20N to the right for A to remain at rest (the max might be a lot higher). But does this produce an equal and...
  46. A

    Will Box Y Remain in Equilibrium?

    Homework Statement A 8-kg homogeneous box X is resting against another 20-kg homogeneous box Y at an angle such that its diagonal BC is horizontal as shown in Figure Q1. The angle of static friction between box X and the floor is 45° and that between box Y and the floor is 30°. Treat the...
  47. V

    Kinetic friction or static friction

    Can anyone explain this case ? If a moving box is pulling with a force F and the kinetic friction is 0.4F, of course, it will move in the direction of applied force with an acceleration and the net force is 0.6F But what if the force suddenly decreases to 0.3F ? The box is still moving so the...
  48. O

    What is the maximum force of static friction for the block?

    Homework Statement A string is tied to a 4.4 kg block and 120g hanging bucket. Students add 20g washers one at a time to the bucket. The student are unaware that the coefficient of static friction for the block on the table is 0.42. A) what is the maximum force of static friction for the...
  49. O

    Static Friction String Problem

    Homework Statement Two objects are made of identical material and are tied together with string. The first object has a mass of 5.0kg and the second object has a mass of 3.0kg. Students measure the maximum force of static friction as 31.4N to move both objects across a horizontal surface. a)...
  50. E

    What Is the Coefficient of Static Friction on a 17 Degree Incline?

    1. A 1760 N force pulls a 266 lg load up a 17 degree incline. What is the coefficient of static friction between the load and the incline? 2. Coefficient of station friction = Force(Static)Max / Normal(supporting) force The Attempt at a Solution
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