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. M

    Static Friction, Kinetic Friction and Rolling Resistance query.

    Hypothetically, if I had a sphere and a block (of the same mass and material (hence the same coefficients of static friction for both interfaces) both stationary on a surface, they would require the same force to initiate motion? Once moving, a coefficient of sliding friction is employed in...
  2. S

    Static Friction of hollow sphere rolling up incline

    For hollow sphere rolling up incline: I know that the kinetic friction will equal 2/3 acceleration since: μgcosθ=2/3a acceleration = 3/5gsinθ so...kinetic friction = 2/5gsinθ But how I do calculate the force of static friction??
  3. S

    Static friction vs kinetic friction (Very simple question)

    This isn't part of a homework question or anything, i was just curious If an object is at rest, static friction is at work, so for an object to move, on a flat surface, force applied must be greater than the static friction force yes? But this is not true for kinetic friction, where an...
  4. K

    Static friction over driven roll, slippage issue /paper machines/

    Hello All, on paper machine which I work we have such configurations as is showed on the sketch: http://imageshack.us/photo/my-images/706/systemt.jpg/ a forming fabric (wire) is driven by two rolls, couch roll (with two suctions chamber) and so called FDR (forward drive roll). On the...
  5. S

    Can someone help me with this static friction problem?

    Homework Statement A 45-kg crate is placed on an inclined ramp. When the angle the ramp makes with the horizontal is increased to 24 degrees , the crate begins to slide downward. What is the coefficient of static friction between the crate and the ramp? Homework Equations \SigmaF=ma...
  6. P

    Coefficient of Static Friction with Acceleration

    Homework Statement A car can decelerate at -4.90 m/s^2 without skidding when coming to rest on a level road. What would its deceleration be if the road were inclined at 11° uphill? Assume the same static friction coefficient. Homework Equations Force of Static Friction / Normal Force...
  7. F

    Need help calculating angle with coefficient of static friction

    There's a box sitting on a plank. The coefficient of static friction is 0.33. I want to figure out at which angle the box will begin to slide if the plank is tilted. I know the factors that come into play are FN, Fg or Fgx, and Fs. So far I have Fnet= FN-Fs-Fg =FN- μs-sin∅...
  8. F

    Calculating angle with coefficient of static friction value

    There's a box sitting on a plank. The coefficient of static friction is 0.33. I want to figure out at which angle the box will begin to slide if the plank is tilted. I know the factors that come into play are FN, Fg or Fgx, and Fs. So far I have Fnet= FN-Fs-Fg =FN- μs-sin∅ =cos-0.33-sin∅...
  9. R

    Static friction on banked curve

    If a curve with a radius of 89.0m is perfectly banked for a car traveling 71.0km/hr, what is the minimum coefficient of static friction for a car not to skid when traveling at 91.8km/hr? I figured out theta = 24. 03degs from the equations F(normal)*cos(theta) = mg and F(normal)*sin(theta) =...
  10. P

    Level 3 Forces Problem - Coefficient of Static Friction

    Homework Statement A coffee cup on the dashboard of a car slides forward on the dash when the driver decelerates from 48 km/hr to rest in 3.7 s or less, but not if he decelerates in a longer time. What is the coefficient of static friction between the cup and the dash? Homework...
  11. Z

    Calculating Minimum Force to Prevent Slipping on an Inclined Plane

    I've worked through this problem for a while now and can't quite come up with an answer. The problem is as follows: A block with mass 5 kg sits on an inclined plane of 30°. The coefficient of static friction is 0.1 between the plane and block. A force F is applied in the horizontal direction...
  12. K

    Calculating Static Friction and the Coefficient of Friction

    *** Title says static - need kinetic friction!Homework Statement Find the amount of kinetic friction. A block with mass of 0.422kg slides down a ramp from rest. Given: acceleration = 1.58m/s^2, mass = 0.422kg, theta = 29.0°, velocity two (end): 1.7m/s, and total time is 1.10s. I also need to...
  13. P

    Question about static friction and energy loss

    I know static friction can cause an object to accelerate, but also decelerate. And i also know that static friction never cause energy loss, but I wonder when it causes an object to decelerate, its kinetic energy should decrease, so where is the mechanical energy gone? Has static friction done...
  14. C

    Static Friction: Max Force Magnitude Applied?

    Homework Statement Which of the following statements are true about Fs, max in the equation mu=Fs, max/Fnormal? I. Fs, max is exerted perpendicular to the surfaces in contact. II. Fs, max represents the maximum value of the force of static friction. III. On a level surface, the magnitude of...
  15. M

    Coefficient of static friction of uniform rod

    Homework Statement A uniform rod AB has a length l and a weight W0. End A is in contact with a rough wall, but it is not fixed. A massless cord connects end B and is fixed to the wall at point C. The rod AB is now horizontal and the angle formed between the cord and rod is θ as shown in the...
  16. S

    Finding the Coefficient of Static Friction

    1. A wooden block of mass 29.0 kg sits on a horizontal table. A wire of negligible mass is attached to the right side of the block and goes over a pulley (also of negligible mass and frictionless), where it is allowed to dangle vertically. When a mass of 15.5 kg is attached to the dangling wire...
  17. T

    Statics : find coefficient of static friction

    Homework Statement Find coefficient of static friction if shell starts to slip at θ = 60° known - θ unknowns - P, r, Normal force, weight Homework Equations friction = μ * normal force The Attempt at a Solution I do not know where to start. It looks like the picture wants you to...
  18. Q

    Static friction with wedges problem

    Homework Statement http://www.solutioninn.com/images/E-C-S%20%28808%29.PNG ignore the given FBD below the pic. Problem said that: there are 3 blocks like in the picture, with weight A = 600lb, B =150 lb, and C = 500. Find force P such that it will move block C. (everything is static...
  19. J

    Static Friction Ladder Problem

    Homework Statement See attachment. Homework Equations F = μN The Attempt at a Solution I attached the FBD I drew. I then did ƩFx = FA + FBcosθ - NBsinθ = 0 ƩFy = NA -W + NBcosθ + FBsinθ = 0 ƩMA = 19.5NB - 3.75W = 0 ƩMB = 3.75W - 7.5NA + 18FA = 0 FA = μNA FB = μNB θ =...
  20. K

    Does Static Friction Ever Perform Work?

    Homework Statement "The work done by static friction can be: a) positive b) negative c) zero d) nonnegative e) any of the above Homework Equations W=F*d F(friction)= μ *FN The Attempt at a Solution I thought the answer must logically be "c) zero" because static friction has no distance...
  21. S

    Static Friction Coefficient of 224 kg Crate on 20.1° Incline

    Homework Statement A 224-kg crate rests on a surface that is inclined above the horizontal at an angle of 20.1°. A horizontal force (magnitude = 543 N and parallel to the ground, not the incline) is required to start the crate moving down the incline. What is the coefficient of static friction...
  22. S

    Find coefficient of static friction

    The problem: A car traveling on a flat (unbanked) circular track accelerates uniformly from rest with a tangential acceleration of 1.60 m/s2. The car makes it one quarter of the way around the circle before it skids off the track. Determine the coefficient of static friction between the car and...
  23. R

    Finding the Relationship between Static Friction and Normal Force

    Homework Statement So I have this lab I have to do about finding the relationship between static friction and normal force. So basically I need to find find how the Static Friction and Normal Force relate by doing a lab experiment. The materials I have are: Spring balance / scale Weights...
  24. S

    Static Friction and Centripetal Force

    Hi, I am very confused. I have searched everywhere online and have drawn free-body diagrams, but I am still confused as to why static fricition, not kinetic friction, provides the centripetal force in a car moving in a circle. In addition, assuming that the centripetal force of a car...
  25. M

    Direction of static friction for an object on a car that is in circular motion

    Can someone please explain why static friction points in the same direction as the centripetal force for an object (like a box) on the flatbed of the truck that is traveling in uniform circular motion? Thanks in advance. :)
  26. T

    Static friction and kinetic friction, solve for acceleration and force.

    Homework Statement A 62 kg crate is dragged across a floor by pulling on a rope attached to the crate and inclined 16° above the horizontal. (a) If the coefficient of static friction is 0.57, what minimum force magnitude is required from the rope to start the crate moving? (b) If μk = 0.31...
  27. H

    Coefficient of static friction between a ladder and a friction-less wall

    Homework Statement A uniform 7.7 m tall aluminum ladder is leaning against a friction-less vertical wall. The ladder has a weight of 291 N. The ladder slips when it makes a 59.0◦ angle with the horizontal floor. Determine the coefficient of static friction between the ladder and the floor...
  28. M

    Is Static Friction Always Present as a Force?

    I'm a bit confused about the presence of a static friction FORCE. So here's the question: The potential for static friction is always present due to the nature of the contact surfaces and the normal force. But is a static friction FORCE always present or does it arise in response to...
  29. K

    Static friction of ration of wheel

    Homework Statement A constant horizontal force F of magnitude 10N is applied to a wheel of mass 10 kg and radius 0.3 m. The wheel rolls smoothly and the acceleration of its center of mass is 0.6 m/s^2. What is that frictional force on the wheel?The Attempt at a Solution ok so the frictional...
  30. H

    Circular Motion with static friction of race car

    Homework Statement In Formula 1 race, the cars approach curves from the outside, cut through to the inside, and then drift again to the outside (red path AA’ in the figure). However, the blue path (BB’) in the figure is shorter. Then why do not the drivers follow the shortest path? Give...
  31. S

    A banked roadway with static friction

    Homework Statement A car rounds a banked curve. The radius of curvature of the road is R, the banking angle is θ, and the coefficient of static friction is μ. a) Determine the range of speeds the car can have without slipping up or down the road.Homework Equations Newton's second law, as...
  32. L

    Finding the Coefficient of Static Friction in the Real World

    I remember doing an experiment in Physics class to find the coefficient of friction with gravity. We set an object with a flat surface on top of a ramp, and adjusted the ramp angle so that the object would move down the ramp at a constant velocity. Then we measured the angle of that ramp to find...
  33. A

    Static Friction and Frictional Force Ranking Task of Crate

    Below are six crates at rest on level surfaces. The crates have different masses and the frictional coefficients [the first value is the static friction and the second is the kinetic friction] between the crates and the surfaces differ. The same external force is applied to each crate, but none...
  34. M

    What is the necessary force to move a crate on a rough surface?

    Homework Statement To move a large crate across a rough floor, you push on it with a force F at an angle of 21° below the horizontal, as shown in the figure. Find the force necessary to start the crate moving, given that the mass of the crate is m = 37 kg and the coefficient of static friction...
  35. L

    Static friction on a car on a circle

    When a car is moving on a circular track which is sloped away from the centre of the track, is the static friction keep that car on the circle (constant speed) towards the outside of the circle, opposite the acceleration? I'm having trouble seeing this because to me, the car would want to...
  36. M

    Magnitude of kinetic friction and static friction

    Homework Statement A 12g coin slides upward on a surface that is inclined at an angle of 14degrees above the horizontal. The coefficient of kinetic friction between the coin and the surface is 0.25; the coefficient of static friction is 0.40. Find the magnitude of the force of friction when...
  37. D

    Force applied perpendicular to velocity, kinetic or static friction?

    The other day, we were discussing cars going through turns and the max speed they could do without slipping. My teacher asked us if static or kinetic friction should be used. I answered static, because the wheels are rotating and thus not sliding over the road surface. He ended up saying the...
  38. M

    Force of a spring and static friction

    Homework Statement A backpack full of books weighing 54.3N rests on a table in a physics laboratory classroom. A spring with a force constant of 200N/m is attached to the backpack and pulled horizontally, as indicated in the figure. If the spring is pulled until it stretches 1.50cm and the...
  39. J

    Newton's Laws and coefficient of static friction

    A 5.00-kg block is placed on top of a 12.0-kg block that rests on a frictionless table. The coefficient of static friction between the two blocks is 0.600. What is the maximum horizontal force that can be applied before the 5.00-kg block begins to slip relative to the 12.0-kg block, if the force...
  40. C

    Mass of Block 1 & Static Friction Info for Block-Table System

    Block 1 as shown in the link below(url) has a mass of 10.3 kg. The coefficient of static friction between the block and the table is μs = 0.36 and the coefficient of kinetic friction is μk = 0.336. a) What should the mass of the second block be so that m1 is just on the verge of sliding? I...
  41. T

    Understanding Static Friction in a Cart and Wall System

    A cart (with wheels) sits on a horizontal table. The front of the cart is a vertical wall, with mass M = 0.313 kg held against the wall. You want to push the cart forward with an acceleration of magnitude a so the mass M can be released and it will not slide down the wall. Assume the coefficient...
  42. C

    Static Friction but no mass given Help

    Homework Statement The coefficent of static friction between the floor of a truck and a box resting on it is 0.36. The truck is traveling at 70.0 km/hr. What is the least distance in which the truck can stop and ensure that the box does not slide? Professor gave us these clues: It is...
  43. X

    Static friction and centripetal force

    Homework Statement "If the coefficient of static friction between the block of mass m and the turntable is \mu_s, determine the maximum constant angular velocity of the platform without causing the block to slip." I'm actually using this problem to understand why I'm getting the wrong answer...
  44. P

    Finding coefficient of static friction with velocity and radius

    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 m...
  45. H

    Static friction coefficient question

    Homework Statement from giancoli 5th ed (algebra based) chapter 4, question 42 Drag race tires in contact with an asphalt surface probably have one of the higher coefficients of static friction in the everyday world. Assuming a constant acceleration and no slipping of tires estimate...
  46. P

    Finding angle with just static friction coefficient

    Homework Statement m = 10kg static friction coefficient (Us) = 0.4 angle = ? Homework Equations If the coefficient of static friction is 0.4, calculate the angle at which the box begins to slide down the plank as it tilts. The Attempt at a Solution m = 10kg Us = 0.4 angle...
  47. W

    Upward Force required to break static friction

    Homework Statement What is the upward force required to make pipe start to move? There is a fixed point and a 36 inch shaft. The force would be applied 36 inches away to the point. The load is 1700lbs. The end point only needs to come up enough so that the static friction of the pipe is...
  48. I

    Simple Harmonic Motion and Static Friction. I am stumped.

    Homework Statement During an earthquake, a floor oscillates horizontally in approximately simple harmonic motion. Assume it oscillates at a single frequency with a period of 0.84 s. After the earthquake, you are in charge of examining the video of the floor motion and discover that a box on...
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