Force of friction Definition and 140 Threads

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

    Force of friction and Torque problem

    Hi all, I'm a new member here. I've encountered a lot of help from searching through this website! I've searched through several threads dealing with friction and torque on here, but still can't quite figure out this problem... Homework Statement A plot of \tau vs. \alpha has a vertical...
  2. M

    Inclined Planes; Finding Force of Friction

    Homework Statement A 275 N box is sliding down a frictionless inclined plane. If the incline makes an angle of 30.0 degrees with the horizontal, what is the acceleration along the incline? I don't need to know how to figure out the solution to this problem - yet, atleast. Im trying to...
  3. L

    When does Force of Friction = Fnet

    Just need to know, when does Force of Friction = Fnet
  4. D

    Inclined plane and force of friction

    Homework Statement I am having some difficulties finding out the force of friction for an inclined plane. If we know the mass of the object, the angle of the inclined plane, and the acceleration, how to we find Ff? I know how to draw the diagrams, but I can't seem to find what force of...
  5. N

    How Do I Find the Force of Friction for My Lab Report?

    Homework Statement Ok, I am doing attempting to do a lab report right now and I am unable to find the forces that I need. This is what i am being asked to do: "Plot the force (not mass) applied by the sand versus the force exerted on the track by the block and its load for both the...
  6. P

    Solving Physics Homework: Force of Friction & Work Done

    Homework Statement Joe puts 11400 J of energy to drag crate 25 m across floor with constant speed. Rope makes 48 degree angle with horizontal. Force exerted by the rope on the crate? What is the force of friction acting on the crate to impede its motion? What work is done by the floor...
  7. X

    How can I calculate the force of friction on a rocket launched at school?

    I have to find the force of friction against a rocket that we launched at school. How would I do that? I know coefficient = Friction/Fn I only have Fn, how do I find the frinction? I'm really lost :(
  8. B

    How Does the Force to Start and Maintain Car Movement on Asphalt Differ?

    Homework Statement A car of weight 1500 N has its brakes locked. Calculate the force needed to begin to drag he car on dry asphalt. How will the force needd to slide it along the asphalt compare with the force needed to start sliding it? Why? (Static coefficient=1.2, Kinetic coefficient=0.8)...
  9. B

    What is the magnitude of force of friction of the snow

    seld pulled at a constant velocity acroos a horizontal snow surface, if force 80 apploed to the sled rope at an angle of 53 to the ground, what is the magnitude of force of friction of the snow? i don't know how to solve it i have test 2morrow i need some explanition plez
  10. P

    What is and how do we derive force (F) opposite the force of friction (Ff)?

    Sum of all Forces= Force - Force of Friction We have Formulas to use in our physics test for an object on an inclined plane w/ friction: Sum of all Froces= F-Ff, Sum of all Forces=ma, a=(Sum of all Forces)/m Ff=Uk(N) and Sum of all...
  11. A

    Work of pushing box horizontally - including force of friction

    Homework Statement A man slides a 100.0 kg box along the floor for a distance of 4.0m. If the coefficient of kinetic friction is 0.250, and the man does the job in 3.6s, what is his power output in watts? Homework Equations W=Fd P=W/t The Attempt at a Solution I don't know how...
  12. A

    Ladder Question - Force of friction required to prevent ladder from slipping

    Homework Statement A uniform 15kg ladder whose length is 5.0 m stands on the floor and leans against a vertical wall, making an angle of 25 degrees with the vertical. Assuming that the friction between the ladder and the wall is negligble, what is the minimum amount of friction between the...
  13. M

    Calculating Forces of Friction with Coefficient of 0.544 and Weight of 86.5N

    The board which weighs 86.5N is sandwiched between two other boards. If the coefficient of friction between the boards is 0.544, what must be the magnitude of the horizontal forces acting on both sides of the center board to keep it from slipping downward? [b]2. Force of friction =...
  14. H

    Average Force Of Friction (attempted Question)

    Homework Statement find the average of a block being propelled propelled by an elastic band. We know it is uniform acceleration. my attempt on this problem Measure the force applied of elastic band with a Newton scale. The more you strecth the farther the distance the block will travel...
  15. H

    Average force of friction help

    Homework Statement hi guys, i am having trouble with this problem. Calculate the average force of friction acting on a wood block as it is propelled along the floor by an elastic band ? my solution and my ideas: What does it mean by average froce of friction? I first weighed the piece...
  16. K

    What is the magnitude of the upward force of friction

    [COLOR="Navy"]:confused: hi guys :eek: please help I am really confuzzeled
  17. N

    HELP problem involving force of friction and normal force

    A 2.5 kg block is initially at rest on a horizontal surface. A horizontal force of magnitude F = 6.0 N and a vertical force of magnitude P are then applied to the block. The coefficients of friction for the block and surface are μ_s = 0.40 and μ_k = 0.25. Determine the magnitude of the...
  18. M

    Solving Force of Friction for Homework

    Homework Statement A sled pulled out a constant velocity across a horizontal. If a is a horizontal force of 8.0 x 10^1 N is applied at an angle of 53 degrees in the ground. What is the force of friction between the sled and the snow? Homework Equations I convert the N into grams...
  19. S

    I need the normal force, the force of friction, and her acceleration

    I've got 2 problems: Number 1: Greg is pushing a 32 kg crate across the floor. He is making like difficult by applying his 800 N force down at an angle of 37 degrees below the horizontal. The coefficient of kinetic friction between the crate and the floor is .50. I need to find the normal...
  20. J

    Force of friction of this cart on wheels with a motor driven propeller

    can anyone show me how to solve this problem? a cart on wheels with a mass of 250 g has a motor driven propeller with a force P of .3 N, and it moved down an incline of 30 degrees with an acceleration of 3.5 m/s^2. What is the force of friction ? determine coefficent of friction
  21. J

    Cart with propeller - Find force of friction

    can anyone show me how to solve this problem? a cart on wheels with a mass of 250 g has a motor driven propeller with a force P of .3 N, and it moved down an incline of 30 degrees with an acceleration of 3.5 m/s^2. What is the force of friction ? determine coefficent of friction
  22. Z

    Force of friction with multiple coefficient of frictions

    I'm working on this problem for homework. Basically it's to find the work done by friction. Now for the work it would be the force of friction times the displacement. The problem is the board being pushed is going over 2 different surfaces, with 2 different values for friction, at the same time...
  23. Z

    Calculating Force of Friction on 8.1g Bullet in Rifle Barrel

    please help me FRICTION A 8.1g bullet leaves the muzzle of a rifle with a speed of 605.8m/s. What constant force is exerted on the bullet while it is traveling down the0.5m lengthof the barrel of the rifle? answer in N. Thanks in advance!
  24. M

    Force of Friction: Solving for 15 kg Child on 4.0m Slide at 40 Degrees

    This is my problem A 15 kg child slides, from rest, down a playground slide tht is 4.0 m long, as shown in the figure. The slide makes a 40 degrees angle with the horizontal. The child's speed at the bottom is 3.2 m/s. What was teh force of friction that the sldie was exerting on the...
  25. K

    How Do You Calculate the Force of Friction for a Moving Car?

    This is probably horribly easy, but it's almost 1 AM so I'm going nutty trying to figure this one out. The questoni: "A 2000kg car is traveling at a constant 30m/s with the motor producing a force of 4000 N forward. Find the force of friction." I drew the diagram. Is acceleration 0...
  26. V

    Calculating Force of Friction on a Bicyclist

    with a terminal speed of 0.2 mm/s. The particle has a mass of 10^-10 g and a retarding force of the form bv. What is the value of b? i converted everything to SI and i got -4.905e-08 kg/s but it is wrong.. am i close? another question... A bicyclist travels in a circle of radius 26 m at a...
  27. E

    Force of Friction: Calculating Car's Acceleration

    I'm stuck! Please help! I have been looking @ this problem for 2 hours! :rolleyes: A 1200 kg car has a speed of 30 m/s - it runs out of gas and coasts, stopping in 40 secs. What is average force of friction on the car? Do you find the car's acceleration first? There is no force, so you...
  28. F

    Calculating Average Force of Friction on a Roller Coaster

    Question: Determine the average force of friction over the first drop and over the entire trip from top to bottom. This is a question of have from a lab experment which was when we designed a "roller coaster" for a ball (it was a downwards ramps with 2 humps on it). I have the actual...
  29. T

    Is the Normal Force Correct in Your Friction Work Calculation?

    A 19.1 kg block is dragged over a rough, hor- izontal surface by a constant force of 195 N acting at an angle of angle 29.1 degrees above the horizontal. The block is displaced 30.3 m, and the coeficient of kinetic friction is 0.116. The acceleration of gravity is 9.8 m/s^2 . the...
  30. T

    How Does Friction Affect the Motion of a Spring-Attached Block?

    a block of mass 10kg is attached to a spring with a constant of 1850 N/m. the coefficient of sliding friction between the block and the surface is .25 the block is pulled back 11 cm to the right and released. the question asks the speed at different points, and how far the distance after...
  31. G

    How do you calculate the force of friction on an inclined plane

    How do you calculate the force of friction on an inclined plane(ramp) a certain number of degrees from the horizontal?(Which formula is used) Mass of block = 10 Kg Angle of incline = 30 degrees Coefficient of friction = 0.25 Gravity = 9.8m/s2 What is the acceleration of the blockdown...
  32. U

    Velocity related to force of friction

    A 5kg object slides 100m down a frictionless inclined plane dropping 45m. It then slides along a horrizontal surface with a coefficiet of kinetic friction of .75 intil it stops. How long does it take to stop after it leaves the inclined plane? I'm not sure how to get the time. Here's what I...
  33. N

    Help with Physics Problem: Calculating Force of Friction

    i need any help that anyone can give me... i understand some things in physics, but i don't get the big picture, and I am really not sure of how to do things, and i am really confused about this one problem in particular... it states: a tractor uses a chain to drag a 675kg tree along the...
  34. B

    What Is the Coefficient of Kinetic Friction for a Two-Mass System on an Incline?

    masses m1=4.00kg and m2=9.00kg are connected by a light string tht passes over a frictionless pully. m1 is held at rest on the floor and m2 rests on a fixed incline of 40.0degrees. the masses are released from rest, and m2 slides 1.00m down the incline in 4.00seconds. determine the acceleration...
  35. K

    Find Force of Friction for 990 kg Car on 4° Incline

    Any help? A(n) 990 kg car is parked on a 4 degrees incline. The acceleration of gravity is 9.8 m/s^2. Find the force of friction keeping the car from sliding down the incline. Answer in units of N.
  36. A

    What happens to force of Friction when Force of Gravity is DOUBLED?

    would the force of gravity also double? and what about when the force of gravity triples, then what would happen to the force of friction? Would it be the same down the road, like for example, when it quadruaples, would the force of friction also quadruaples..and have a direct relationship btw...
  37. P

    Ways to find force normal in relation to force of friction

    Please tell me some ways to find force normal in relation to force of friction.
  38. P

    What is the Equation for Force of Friction?

    I think the reason that my problems have arisen is because of my equation for the force of friction. I have Ff= ucosAngle That right?
  39. K

    Force of friction in circular motion

    I'm having trouble with the following problem: If a curve of radius 80.0 m is perfectly banked for a car moving 70.0 km/hr, what must be the coefficient of friction in order to prevent skidding when the car is moving at 90.0 km/hr. OK, I know that I need to find the angle of the "perfectly...
  40. H

    SIMPLE force of friction question

    You are pulling a 15kg wagon by the handle (with 5N of force) forming a 45 degree angle level to the ground. What is the force of friction on the wagon? Okay, is it just me, or does this problem seem way to easy to be worth 100 pts? It's -3.54N, right? Is the weight of the wagon irrelevant...
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