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. T

    Coefficient of static friction of clothes

    Problem: A top-loading washing machine has a spin cycle that rotates at 8.5 cycles per second. The spinning drub that holds the clothes has a radius of 35 cm. What is the linear speed of the clothes? ω = (8.5 cycles/s) / (2pi rad) = 53.4 rad/s v = ωr = (53.4 rad/s) * (0.35 m ) = 19 m/s...
  2. M

    Finding the Coefficient of Static Friction on a Banked Curve

    Homework Statement If a curve with a radius of 87.5 m is perfectly banked for a car traveling 71.8 km/hr, what must be the coefficient of static friction for a car not to skid when traveling at 93.8 km/hr? Homework Equations tan \theta = v^{2} / r*g The Attempt at a Solution I...
  3. H

    Coefficient of static friction

    Homework Statement If a curve with a radius of 77.0 m is perfectly banked for a car traveling 65.8 km/hr, what must be the coefficient of static friction for a car not to skid when traveling at 91.2 km/hr? Homework Equations \mus = v^2/(g*r) The Attempt at a Solution 1 Incorrect...
  4. B

    Static Friction Coefficient

    Homework Statement To test the performance of its tires, a car travels along a perfectly flat (no banking) circular track of radius 412 m. The car increases its speed at uniform rate of, at= 4.14m/s^2, until the tires start to skid. If the tires start to skid when the car reaches a speed of...
  5. H

    Friction Forces (Static Friction)

    Homework Statement A boy has stacked two blocks on the floor so that a 5.0 kg block is on top of a 2.0 kg block. 1. If the coefficient of static friction between the two blocks is 0.40, and the coefficient of static friction between the bottom block and the floor is 0.22, with what force...
  6. M

    Pushing books - force, kinetic and static friction

    Homework Statement A woman attempts to push a box of books that has mass 36.5 kg up a ramp inclined at an angle 27.5 degrees above the horizontal. The coefficients of friction between the ramp and the box are mu_s and mu_k. The force F applied by the woman is horizontal. Assume that mu_s is...
  7. M

    Pushing blocks - static friction, force, and accel

    Homework Statement A block of mass 1.2 kg rests on top of another block of mass 1.8 kg, which rests on a frictionless surface. The coefficient of static friction between the blocks is mu_s = 0.3. (a) What is the maximum horizontal force that can be applied to the upper block so that the...
  8. M

    Coefficient of static friction with radius, speed, etc. given

    Homework Statement To test the performance of its tires, a car travels along a perfectly flat (no banking) circular track of radius 331 m. The car increases its speed at uniform rate of at ≡ d|v|dt = 3.68 m/s^2 until the tires start to skid. If the tires start to skid when the car reaches a...
  9. J

    Homework help coeff of static friction

    Homework Statement You are in a car accelerating the car at 15 m/s^2 without spinning tires out. determine the minimum coeff of static friction between the tires and the road to make this possible Homework Equations The Attempt at a Solution
  10. P

    How Can You Measure Static Friction Without a Spring Balance?

    how can i find static friction...if i don't have a spring balance of any material to find it...pls help!we need this to our defense...thank you...:shy:
  11. M

    Static friction of blocks on a wire

    Homework Statement 2 blocks are connected with wire each on its own angle area. Body 1 (B1) has weight 900N, angle 30, µ = 0,35 B2 wight = 1100N, angle 45 and µ=0.30 There is no friction on at the T ( picture ) How big F has to be to pull block1 down following shown path? Homework...
  12. Y

    Calculating the Force of Static Friction on a 2000kg Car

    Homework Statement A 2000kg car makes a left run of radius 6.5 m. If this turn is made in 2 seconds, what isthe force of static friction of the car during the turn? Homework Equations a = v^2/r, F = (m*v^2)/r ; d = v*t; The Attempt at a Solution d/t = v = 3.25 m/s Fc =...
  13. B

    Minimum Coefficient of static friction to keep a block from sliding?

    A 5kg block is placed on top of a 15kg block that rests on a frictionless table. The surface between the top and bottom blocks is roughened so that there is no slipping between the blocks. A 40N horizontal force is applied to the top block. What is the minimum coefficient of static friction...
  14. A

    Applied Force ,Kinetic Friction, Static Friction involving two stacked masses

    Homework Statement A block of mass m1 = 2.0 kg is stacked on top of a block of mass m2 = 3.0 kg which is resting on top of a table Both blocks and the table are made of the same material; so the coefficients of friction between all surfaces are the same They are (attempt at a mew) ms = .60...
  15. E

    Banked Curve Algebra With Static Friction

    Homework Statement 9. A 2000 kg car is racing around a banked circular path whose radius of curvature is 50.0m. The coefficient of static friction between the car and the road is 0.100. What is the maximum possible speed for the car to remain on the road if the angle of the curve is 15°...
  16. U

    Mechanics, Static friction and springs

    Homework Statement A block of mass m lies on a rough surface, inclined at angle theta to the horizontal. It is attached to a spring of force constant; the other end of the spring is fixed to a point on the table below the inclined block. The co-eff of static friction is mu-s and kinetic...
  17. P

    Understanding Frictional Forces in Rotational Motion

    Homework Statement A spool rests on a horizontal surface on which it rolls without slipping. The middle section of the spool has a radius r and is very light compared with the ends of the cylinder which have radius R and together have mass M. A string is wrapped around the middle section so...
  18. K

    Question about Static Friction

    Okay, I have been coming across a lot of problems that share something in common; They all ask what is the minimum amount of force required to move the object. Alright, so I've been looking all over the internet and have been finding varying answers from If the Pushing force (P) equals Fsmax...
  19. K

    Maximum speed of a car in a circular flat track (involves static friction)

    Homework Statement In a circular flat track of radius 50m, what is the maximum speed car can go without sliding? Assume the coefficient of static friction between the car tire and the road is 0.4. Homework Equations Unsure of what equations to use. The Attempt at a Solution Unsure...
  20. D

    Static friction on inclined surface

    Hello all. I'm having issues trying to figure out the following problem. A boy with a mass of 52 kg and on a 56-degree slope is hanging on to a cord with a breaking strength of 152 Newtons. What must be the coefficient of static friction between the boy and the surface?
  21. A

    Circular Motion and Static Friction

    Homework Statement A small metal cylinder of mass m=0.20 kg sits on a rotating turntable. The coefficient of static friction between the metal cylinder and the turntable is us=.08. The cylinder is located 0.15m from the center of the turntable. Find the maximum speed that the cylinder can...
  22. S

    Calculating the Coefficient of Static Friction

    Homework Statement A 25 kg chair intially at rest on a horizontal floor requires 365 N horizontal force to set it in motion. Once the chair is in motion, a 327 N horizontal force keeps it moving at a constant velocity. A: Find the coefficient of Static Friction between the chair and the...
  23. M

    Static friction on an inclined plane.

    Homework Statement http://img124.imageshack.us/img124/9997/problem3.jpg Homework Equations f=mgcos theta The Attempt at a Solution I am thinking the answer is f = mgcos theta because gravity only acts on y-component but the answer is f=mgsin theta . Can anyone explain?
  24. J

    How to handle string intersection in static friction calculation?

    Homework Statement a mass m is supported as shown in the figure by ideal strings connected to a rigid wall and to tal mass 3m sitting on a horizontal surface. what is the minimum coefficient of static friction between the larger mass and the surface that permits the system to remain in...
  25. mvantuyl

    How the coefficient of static friction works

    Not exactly a homework problem, but I'm trying to make sure I understand how the coefficient of static friction works. Given an object on an inclined plane and a question which asks for the minimum angle at which the object will begin to slide, I know that the formula to use is: mg...
  26. K

    Kinetic/ Static friction- Newtons 3rd Law

    Homework Statement The coefficient of static friction is 0.60 between the two blocks in figure. The coefficient of kinetic friction between the lower block and the floor is 0.20. Force causes both blocks to cross a distance of 5.0 m, starting from rest. What is the least amount of time in...
  27. S

    Finding actual static friction given mass, external force, and angle.

    1. What is the actual static frictional force that acts on the block if an external force of 25.0 N acts horizontally on the block? ________N The mass of the block is 25.0kg. Assume g=9.80m/s^2 Homework Equations I am using: static frictional force=(coefficient of static...
  28. S

    Coefficient of static friction

    Homework Statement A block of mass m is resting on a horizontal surface whose coefficient of static friction is μs. http://bcs.whfreeman.com/WebPub/Physics/tiplerphysics6e_bridge/question_bank_images/fig5-65.png?2439 Which of the following statements (if any) are true? A. If you...
  29. N

    Bracket/block static friction problem (physics)

    Homework Statement http://img3.imageshack.us/img3/6618/5n6.jpg Image there. Homework Equations Well this is actually where the problem occurs. You make your own equations. The Attempt at a Solution It's the friction that is really messing me up. I'm just so confused, I'm going to...
  30. Z

    Friction problem with banked curve given static friction coefficient

    Homework Statement What is the maximum speed with which a 1200 rubber-tired car can take around a banked curve with radius of 80.0 meters an angle of 19.0 degrees? (static friction coefficient is 1.0) Homework Equations Fs=mu*F(normal) F(netxdirection)/m=acceleration...
  31. S

    Kinetic friction vs static friction?

    OK, so in my physics class we are doing friction. And the book states that static friction usually larger then kinetic. Then he posed a question to whether or not there might be some crazy scenario where the kinetic friction is larger than the static friction? Personally, I cannot think of...
  32. M

    Kinetic friction & static friction

    Homework Statement http://img182.imageshack.us/img182/8174/p560.gif An aluminum block, m1 = 5.00 kg, and a copper block, m2 = 15.36 kg, are connected by a light string over a frictionless pulley. They sit on a steel surface as shown in the figure below, where θ = 30.0°. (See the table...
  33. F

    Is the Coefficient of Static Friction Always Higher than Kinetic Friction?

    One of our new labs states that the coefficient of static friction is USUALLY higher than the coefficient of kenitic friction. Is this true? If so, for what types of materials is the coefficient of static friction less than the coefficient of kenitic friction?
  34. S

    Exploring the Differences between Inertial and Static Friction

    HI guys, i was wondering what is the difference between inertial and static friction? If a car is on a frictionless ground, does it have static friction and the inertial is the same even if it is on a rough surface right?
  35. W

    Static Friction when pushing a crate on the floor

    Homework Statement You try to push a crate of weight M with a force F on a horizontal floor. The coefficient of static friction is μ and you exert the force F under an angle θ below the horizontal. a) Determine the minimum value of F that will move the crate b) Assume you have not...
  36. L

    Two Angle, Leaning Stick Static Friction Problem

    State the Problem End A of a slender, uniform rod of weight w and length L bears on a horizontal surface ash shown, while end B is supported by a cord BC of length L. Knowing that the coefficient of static friction is 0.40, determine (a) the value of theta for which motion is impending, (b)...
  37. S

    Finding an angle given only the Coefficient of static friction

    [b]1. A box sits on a horizontal wooden board. The coefficient of static friction between the box and the board is 0.22. You grab one end of the board and lift it up, keeping the other end of the board on the ground. What is the angle between the board and the horizontal direction when the box...
  38. K

    Calculating Minimum Normal Force for a Climber in a Vertical Chimney

    Homework Statement The 70-kg climber is supported in the "chimney" by the friction forces exerted on his shoes and back. The static coefficients of friction between his shoes and the wall, and between his back and the wall, are 0.80 and 0.60, respectively. What is the minimum normal force he...
  39. O

    Finding Length with rpm and static friction

    Homework Statement A bug crawls outward from the center of a compact disc spinning at 190 revolutions per minute. The coefficient of static friction between the bug's sticky feet and the disc surface is 1.4. How far does the bug get from the center before slipping? Homework Equations...
  40. S

    Static Friction: Energy Conservation Explained

    Ok so this is only my second thread (and post) on this site. My question is that if you push something that doesn't deform very much (like wood) or move because of static friction how is energy conserved. Only going to be in 8th grade so try to keep it simple please. :smile: <-- just...
  41. I

    Static friction between two bodies and a surface

    Homework Statement okay, I know it says be descriptive and all, but I'll present a watered down problem with some insignificant data already calculated by me. my problem is to understand the logic behind the solution, I know the solution, I simply think my textbook is... false. here goes...
  42. J

    Using static friction to find tension

    I am having a lot of problems with the tension/force questions on my homework. Here is the last question I don't understand in my homework set: The drawing shows a circus clown who weighs 860 N. The coefficient of static friction between the clown's feet and the ground is 0.41. He pulls...
  43. S

    Sliding Rod In A Magnetic Field (w/ Static Friction)

    Homework Statement Suppose the rod in the figure has mass m= 0.44 kg and length 26 cm and the current through it is I= 40 A. Part A: If the coefficient of static friction is mus= 0.45, determine the minimum magnetic field B (not necessarily vertical) that will just cause the rod to...
  44. P

    Tangential Acceleration and Coefficient of static friction

    Homework Statement There's a ride called the Cajun Cliffhanger. it's a rotating drum that rotates and makes you stick to the walls. here's are the infomation The diameter is 5.3m the speed is 4.2 seconds per rotation at final speed it takes 10.1 seconds to reach the final speed You have...
  45. K

    Static Friction of Ladder

    Homework Statement A uniform 6.0m long ladder of mass 17.0 kg leans against a smooth wall (so the force F_w exerted by the wall, , is perpendicular to the wall). The ladder makes an angle of 22.0 with the vertical wall, and the ground is rough.Determine the coefficient of static friction at...
  46. J

    Minimum Acceleration for Sliding Cream Pie: Solving Static Friction Problem

    Homework Statement The coefficient of static friction between your hand and a pie is 0.70. if you want to put a cream pie pie in someone's face, what is the minimum acceleration needed to keep it from sliding down your vertical hand? The Attempt at a Solution Im not sure how to go about this...
  47. P

    Coefficient of friction and static friction

    If an object slides down a slope at a constant speed is the coefficient of static friction the same as the coefficient of dynamic friction? If yes, is this true in every situation?
  48. W

    Coefficient of Static Friction on a Banked Curve

    Homework Statement If a curve with a radius of 90 m is properly banked for a car traveling 68 \frac{km}{h}, what must be the coefficient of static friction for a car not to skid when traveling at 98 \frac{km}{h}?Homework Equations I know I need \Sigma \vec{F} = m \vec{a}f_s <= \mu_s N and...
  49. A

    Static Friction & Kinetic Friction

    Problem 1: You need to move a 125-kg piece of furniture in your living room. You and your friend exert a force of 305 N to start it moving. What is the coefficient of static friction between the furniture and the floor? Problem 2: A 20-kg bowling ball slides half way down a lane with a...
  50. M

    Static friction preventing block from sliding

    Homework Statement If the coefficient os static friction between the incline and block is .3, then what is the minimum force,F, needed to prevent the block from sliding? m=20kg theta= 50 degrees Homework Equations Normal force= mgcosx Fs= uk mgcosx The Attempt at a Solution...
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