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

    Static friction being the force that opposes the reaction

    Hi there, I was thinking that static friction works in opposition to a reaction force like the force of a fridge against you as you push it. However, since you are pushing horizontally and friction works against you why is it equal or greater than the reaction force? Will the force get...
  2. A

    B Exploring Energy & Work: Static Friction

    Hello, I have been learning about energy and work in my 100 level physics class and I got to thinking: W = F*d But I'm wondering how this works in the case of static friction. For instance, if I take a really heavy object and apply a force to it that isn't enough to move it, the distance it...
  3. Lily131313

    Calculating Required Force for Pushing Metal Blocks | Static Friction Help

    Homework Statement [/B] In an automatic materials handeling operation, metal blocks of 1.5 kg each are pushed one at a time from bottom of a stack six blocks high. If the coefficient of friction is 0.25, determine the horizontal force required to push. There is a figure bellow. I try to...
  4. Nikhil Rajagopalan

    Work done due to static friction in a boat-man system

    In a classic problem where a man walks along the length of a boat floating on the surface of water without friction, Should the net work done due to static friction between the man and the boat be zero. If the length of the boat is L, its mass being M, and the mass of the man being m, the...
  5. W

    Static friction 2 boxes and force question

    Question: A large box of mass M is pulled across a horizontal, friction-less surface by a horizontal rope with tension T. A small box mass m sits on top of the box. The coefficients of static and kinetic frciton between the two boxes are Us and Uk. find an expreeion for the maximum tension Tmax...
  6. U

    What is the static friction force acting on the object?

    Homework Statement A block sitting on a flat surface has a us of 0.5. The normal force acting on the block is 10N. If someone pushes the block with a horizontal force of 2N. What is the static friction force acting on the object? Homework Equations F=ma fs=usR (less than or equal to)The...
  7. S

    Static friction: Will the box move?

    Homework Statement A 55.0-kg box rests on a horizontal surface. The coefficient of static friction between the box and the surface is 0.300. A force of 156 N is applied to the box directed at an angle of 18.0 above the horizontal. Does the box move? Please help??The Attempt at a Solution 156...
  8. E

    Minimum coefficient of static friction

    Homework Statement If the incline of the driveway is 19 ∘ from the horizontal, what must the minimum coefficient of static friction be between your shoes and the ice? Homework Equations Fs=uN The Attempt at a Solution
  9. K

    Derivation of angle of repose - Friction

    Hi, Recently I came across this image in deriving an equation for angle of repose of an object in an inclined plane: "W" is the weight of the component which acts vertically down. "Rn" is the normal reaction by the inclined plane "W cos alpha" is the component of the weight of the object...
  10. V

    How Do Tension and Friction Forces Interact in a Two-Block System?

    Homework Statement 2 Blocks connected by a string is placed on a rough horizontal floor,the coefficient of friction for block 1 is 0.2 while for block 2,it is 0.1. A force of 8N is applied on block 1 and a force of 1N is applied on block 2.Find the tension in the string and the frictional...
  11. terryds

    Static friction vs kinetic friction in Tablecloth trick

    In the tablecloth trick, if we pull the tablecloth with a great force, the objects on it will stay on the table. But, if we pull it gently, the objects on it will still get along with the cloth movement. I know that if the force exceeds the maximum value of static friction, the objects will...
  12. onemic

    Find the angle of an object on an incline (static friction)

    Homework Statement At a construction site, a small crane is raising two boxes of nails on a plank to the roof. One box has already been opened and is half full, while the other box is new. The boxes, including the nails weigh 10kg and 20kg, respectively, and are the same size. If the...
  13. ChrisBrandsborg

    Finding Acceleration and Stopping Time in a Multi-Block Lifting System

    Homework Statement A lifting system can be modeled as two blocks of mass m1 and m2 hanging from two pulleys, connected by ropes to a third block of mass M = 100 kg, lying on top of a horizontal surface. There is gravity g = 9.80 m/s2. a) Ignoring at first friction, find an expression for the...
  14. Eclair_de_XII

    Finding static friction of a block on a table on a pulley?

    Homework Statement "When the three blocks in Fig. 6-29 are released from rest, they accelerate with a magnitude of ##0.500 \frac{m}{s^2}##. Block 1 has mass M, Block 2 has mass 2M, and Block 3 has mass 3M. What is the coefficient of static friction between Block 2 and the table?" Homework...
  15. marsupial

    Coefficients of kinetic and static friction in a pulley

    Homework Statement A block of mass ## M_1 ## is on an inclined plane (the plane is inclined at 30 degrees), and is attached with a light cord over a light, frictionless pulley to another mass ## M_2 ##. ## M_1 ## is fixed at 5.00kg, and ## M_2 ## can be varied. When ## M_2 = 3.20 kg ##, ##...
  16. A

    Static friction vs. Normal force on an incline

    I have two surfaces that have a coifficent of friction of .6. Disregarding mass (if possible) at what angle would the force of static friction and the normal force be equal
  17. L

    Newtonian physics word problem static friction

    Homework Statement truck moves at 22,5 m/s On board the truck, behind, is a box. the static friction coefficient for the box, is 0,250 with regard to the friction between truck floor and the box floor. calculate the shortest possible stopping distance, such that the box does not slide at...
  18. L

    Coefficient of Static Friction = tan (angle of incline)

    Homework Statement I am trying to prove that the coefficient of static friction is equal to the tan of the angle of incline. (You can find the proof of this from ) I set the angle of incline as my independent variable and had an angle range from 10 to 37.5 degrees. After setting the slope to...
  19. RoboNerd

    Question about finding static friction coefficient

    Homework Statement Two boxes each weighing 900 N are stacked on a horizontal floor. Box A is on the bottom, box B is on the top. The coefficient of static friction between box a and the floor is 0.3. A worker applies a force of 600 N to box b parallel to the floor, and the stack moves together...
  20. A

    Does coefficient of static friction change with angle

    Hi all, I am very confused by this concept. As I searched online, all respondents say that friction decreases as angle increases because normal force decreases. BUT, they don't explain this phenomenon: A block on a ramp is static at certain angle, and after the ramp is raised by a certain...
  21. S

    Question about static friction adjusting itself

    In a situation like this, there are two equilibrium's, For just about to accelerate downwards: mgsinθ - Ffriction - T = 0 For just about to accelerate upwards: T - Ffriction - mgsinθ = 0 Is there a situation where there is no static friction i.e. when mgsinθ = T?
  22. B

    What forces causes the top book to accelerate horizontally?

    Homework Statement A small textbook is resting on a larger textbook on a horizontal desktop. You apply a horizontal force to the bottom book and both books accelerate together. The top book does not slip on the lower book. What forces causes the top book to accelerate horizontally? Homework...
  23. S

    Rotational work done by static friction?

    Homework Statement A disk roll without slipping down a incline plane. Identify the forces acting on the disk, explain qualitatively which of these forces do work. Homework Equations The rotational work is given by W=\int \tau_z d\theta (1) , where \tau_z is the component of the torque...
  24. S

    Rotational work and forces like static friction and tension

    I have a doubt regarding the definition of rotational work, which is as follows W = \int \tau_z d \theta Where \tau_z is the component of the torque parallel to the axis of rotation z. My doubt concerns the fact that, looking at this definition, it seems that any torque which has an axial...
  25. 0

    Coefficient of static friction between load and incline

    Homework Statement A 1790N force pull a 266kg load up a 17º incline. what is the coefficient of static friction between load and incline. Homework EquationsThe Attempt at a Solution Tried several times on notebook but I haven't seemed to solve the problem.
  26. M

    3 part question about angular/tangential acceleration

    Homework Statement Hi all, Assignment due at midnight ET, these are the last questions I'm missing 1. A merry-go-round makes one complete revolution in 15.7 s. A 53.1 kg child sits on the horizontal floor of the merry-go-round 4.3 m from the center. Find the child’s acceleration. The...
  27. P

    Magnitude of static friction force

    Homework Statement A 500 kg ox runs and speeds up by 3 m/s2, but is held back by a 120 kg plow that is attached to its back. Assuming the coefficient of static friction between the horse's hooves and the soil is 0.73, what is the magnitude of the static friction force the soil exerts on the...
  28. E

    Basic force with static friction problem

    Homework Statement A 70-kg skier is in a tuck position and moving down a 20-degree hill. Air resistance applies a resultant force of 15 N against the movement of the skier. The coefficient of friction between the skis and the snow is 0.09. What is the resultant downhill force acting on the...
  29. heartshapedbox

    Minimum force to make box slide down slope

    Homework Statement If m=5.0kg, φ=30◦ and μs =0.87, what is the minimum force needed to make the box slide down the slope? [/B] Homework Equations force of status friction is less than or equal to the normal force multiplied by the coefficient of static friction F,normal=mgcosφ The image...
  30. D

    How to solve for coefficient of static friction with mass

    Its for my final project. We are doing a sliding a textbook down an *incline plane* and we are expected to find coefficient of static friction without using Newton guage, and we are also now allowed to use kinematics. I just need some infomration on how to do this, like a formula or something in...
  31. A

    Does Kinetic and Static Friction Act Simultaneously on a Moving Body?

    When a body is in motion , does kinetic and static friction act simultaneously
  32. Biker

    What is the maximum deceleration for two boxes in a car without them falling?

    Homework Statement If you have 2 boxes over each other in a car that is slowing down . The mass of each one of them is 10kg and Us = 0.4 for all surfaces. What is the maximum deceleration that doesn't make the boxes fall? And will it make different if you change the masses of the objects? 3...
  33. R

    Static friction rotating discs

    Hi everyone This is my first post on the forum. I work in engineering and use this forum to answer questions from time to time. I am looking for confirmation of my understanding of static rotation torque (not something I deal with in day to day work). Imagine 2 identical discs or washers that...
  34. WinterGrascph

    Maximum force pulling a wheel without it slipping

    Homework Statement We have a wheel with [mass = 1.5 kg] and a [radius = 0.06 m]. The static friction thing between the ground and the wheel is 0.3 . WIth how much force can we pull the string spooled around the wheel without the wheel slipping. The string ends at the top of the wheel and we...
  35. W

    Questions about rolling and direction of static friction?

    I have spent quite some time trying to get this, can someone please help me understand this? A plank is being pulled by a constant force F, it rests on top of two identitcal sylinders - there is rolling without slipping. What I don't understand is, why does F(p) - red arrow force, affect the...
  36. W

    In which direction does static friction point?

    As I see it; static friction is what provides the centripetal force, but does it do anything else? When the brother applies tangential force, what will happen with the static friction, because I assume it will start to provide less centripetal force because the tangential speed of the child...
  37. J

    How does static friction slow a car down?

    I am unsure how the process works, can somebody please help me out!
  38. K

    Coefficient of static friction on a ramp?

    Homework Statement A small block sits at the midpoint of a 2.0 m plank lying on a level floor. A student slowly raises one end of the plank until the block starts to slide. At that instant, the raised end is 0.55 m above the floor. Find the coefficient of static friction between block and...
  39. P

    Equilibrium and find static friction

    Homework Statement Homework EquationsThe Attempt at a Solution I had someone help me with this problem (not on here) and their process and units don't seem to match to me. Or is this correct?
  40. J

    Direction of Kinetic Friction and Static Friction

    Can someone please explain me the direction of static friction? I know kinetic friction is always going against the motion of an object but for static friction it depends.
  41. T

    Static friction of a block on an incline?

    Homework Statement We are dealing with a block on an incline that you can alter the angle with. The inclination angle was increased until we reached a certain angle(critical angle) that the block just begins to slide at. Use this critical angle and your previous answers for the normal force...
  42. snacksforsale

    How does rotational motion influence static friction?

    I apologize in advance for not exactly adhering to the template, but the question I have here arose from my attempts to solve the following exercises, so please bear with me. (Edit: I also apologize if discussion of a concept belongs in a different forum, as this is not exactly a homework...
  43. D

    Is mgsinθ=static frictional force on an inclined plane?

    According to Newton's 3rd law, for every force there's an equal opposing force. Since a block is sitting on an inclined plane, wouldn't that mean the static friction is acting like the opposing force for mgsinθ thus, mgsinθ=static frictional force? Please respond
  44. TheNeezoMan

    Tension and acceleration of a sled?

    Homework Statement A heavy sled is being pulled by two people as shown in the figure. The coefficient of static friction between the sled and the ground is μs = 0.579, and the kinetic friction coefficient is μk = 0.435. The combined mass of the sled and its load is m = 336 kg. The ropes are...
  45. L

    Question regarding coefficient of static friction

    Hi all, I encounter an un-explainable question during my lab, so I figured it would be a good shot asking here. Also, my English isn't perfect, so if there is anything unclear, say it out and I'm happy to clarify it. In the lab, we placed a sled on a track and slowly lifted one end of the track...
  46. P

    Find minimum value for coefficient of static friction

    Homework Statement Homework Equations Newton's 2nd Law The Attempt at a Solution I was wondering if anyone could verify that I have all the correct vectors or if I am missing any. I just wanted to check before I started trying to derive the equations. [/B]
  47. Chrono G. Xay

    Predicting Initial Length of String Needed Before Stretch

    I have put together an equation whose purpose is: With a desired 'magnitude of static friction' ( μ_s ), 'fundamental frequency' ( f ), and 'tension' ( T ), initial conditions such as 'string breakover angle' ( Θ_0 ), 'nut-tuner distance' ( L_{h,0} ), and 'string diameter' ( d ), and...
  48. erickbq

    [Statics - Torques] Determining Coefficient of Static Friction

    Homework Statement The top of a ladder of L and mass m is connected to a wall by a horizontal cable. The ladder makes an angle Θ=60 with the horizontal. A woman of mass 2m finds that as she climbs the ladder, the ladder begins to slip when she is one-third of the way up the ladder. Find the...
  49. Z

    Finding static friction from circular motion

    Homework Statement A car traveling on a flat (unbanked), circular track accelerates uniformly from rest with a tangential acceleration of 1.70 m/s2. The car makes it one-quarter of the way around the circle before it skids off the track. From these data, determine the coefficient of static...
  50. O

    What happens to acceleration upon exceeding static friction?

    So if I compare how the accelerations are observed in two objects, a car and a block, both having the same mass of 100kg on a surface with μ_{s} = .5 and μ_{k} = .1 Car: The car will have Static Friction Force f_{s} = μ_{s}F_{N}=[μmg = ma] = [.5(100kg)(10m/s^{2}) = 100kg(a)] => so...
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