What is Friction: Definition and 999 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. rudransh verma

    B Understanding Friction: The Impact of Inter-Molecular Bonding on Movement

    Imagine a solid body big and heavy. It will have friction between it and the surface when tried to move. Somehow the cluster of molecules opposes the push. When free these molecules stick on surface and can be moved by a mere blow of wind but when bonded into a solid body the structure of large...
  2. rudransh verma

    B Why does ice have more friction when it's solid compared to when it's melting?

    Water is made up of loose molecules but a body like ice is bonded strongly into a shape. Imagine a ice brick. It will have friction between it and the surface when tried to move. Now it slowly starts melting. The molecules of ice will start sticking on the surface. Somehow the cluster of...
  3. E

    Yes! Calculating Friction Coefficient

    Fg = m * g: Fg = 30 * 9.8 = 294 N Fnet = m * a: Fnet = 30 * 1.2 = 36 N Fax = Fnet + Ff: Fax = 36 + 10 = 46 Fa = Fax / cos(angle): Fa = 46 / cos(25) = 50.75 Fay = Fa * sin(angle): Fay = 50.76 * sin(25) = 21.45 Fn = Fg - Fay: Fn = 294 - 21.45 = 272.55 Ff = mu kinetic * Fn, solving for...
  4. A

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  5. A

    I Understanding Net Internal Torque and Kinetic Friction in a System

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  6. J

    I Direction of friction of each wheel and total moment when a car turns

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  7. P

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  8. Y

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  9. L

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  10. MrS

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  11. S

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  12. A

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  13. G

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  14. rudransh verma

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  15. J

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  16. L

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  17. J

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  18. SpectraPhy09

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  19. rudransh verma

    B Understanding Friction: Causes and Applications in Physics

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  20. P

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  21. A

    I Problem with Static Friction -- Two blocks on a platform

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  22. Send-Help

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  23. S

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  24. L

    B Work and Friction: How Does Fxv Apply?

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  25. Einstein44

    I Coefficient of rolling friction for a lab cart

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  26. J

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  27. Iwanttolearnphysics

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  28. D

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  29. kara123

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  30. G

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  31. vibha_ganji

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  32. TheBigDig

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  33. xWaldorf

    I Friction Coefficient of Marble & Iron on Plastic

    hey, i was looking for information on friction coefficient of marble on plastic and iron on plastic. if you know these values i'll be very glad! thanks in advance
  34. L

    Is there any friction in this case?

    In the experiment, a cart on an inclined plane of 30 degrees is hooked with the force metre by a line. The line is tension T. It is also subjected to the force of gravity Fg. This makes the cart in static equilibrium. But since the cart is hooked with a line, it does not slide down. The net...
  35. DonutHole

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    Fn = 53 X 9.81 X cos 22 Fnet = 524 – 53 X 9.81 sin 22 + μ X 53 X 9.81 cos 22
  36. T

    A Cylinder Rolling in a V-Groove

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  37. Istiak

    Find equation of motion of an inclined plane when there's friction

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  38. mncyapntsi

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    The solution in my textbook says that for b, us = 0.234. However when I use the formula above I get 0.2364 which I feel like is too far off. Something must have gone wrong... Any help would be much appreciated! Thanks :)
  39. T

    Circular motion of a mass on a string on an inclined plane

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  40. T

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  41. L

    Mass m sliding without friction inside a rotating tube

    1) To be in equilibrium, it must be $$\begin{cases}F_{centr}-T=0\\ T-mg=0\end{cases}\Rightarrow F_{centr}=T=mg\Rightarrow m\omega^2 R_0=mg\Rightarrow R_0=\frac{g}{\omega^2}$$ 2) It is intuitive that this equilibrium is unstable but I don't know how to formally prove this. 3) In ##R_0## the...
  42. S

    I Static rotational friction: does diameter matter?

    Imagine a bolted joint with a washer between the bolt and the surface. Assuming the washer is always covered by the bolt head so it's getting a consistent load, does the washer's diameter impact the static friction being imparted on the surface? I see two conflicting ways of viewing this...
  43. O

    Electrical How to estimate friction on the bearings to select motor?

    I'm willing to build a motorized gimbal head for my camera (something like this: https://www.amazon.com/dp/B01JN5D40A/?tag=pfamazon01-20). If my understanding is correct, given that camera will be well balanced on the platform, the motors would not need to hold the load and only should be...
  44. V

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    I am not sure if the explanation below is enough. This is a high school level question. When rubbing occurs between glass and silk, then heat energy is produced which provides the energy needed to free up electrons in outermost orbits of atoms in silk or glass. But silk has very tightly bound...
  45. Dario56

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    When fluid is placed between two parallel plates such that one plate is moving and other is stationary, fluid will start flowing. Between plate and the fluid there is viscous friction given by equation: $$ F = -\eta A \frac {dv} {dy} $$ where $ \eta $ is fluid viscosity, $A$ is area of a plate...
  46. C

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    Dear colleagues, I am dealing with rope friction and the so-called Capstan equation. Situation: A rope wraps around a cylinder with a wrap angle. It depends on the input force. There are very comprehensive approaches by other colleagues, where the friction value depends on the normal force or...
  47. D

    Is Fgy the Same as FN in a System with Two Masses and Friction?

    I am just confused on how to find the normal force/ FN of the first object. My classmates are saying Fgy is the exact same as Fn but I don’t get why Fgy= Fg sin theta Fgy= (20)(9.81) (sin35) Fgy= 112.5 Fgy = FN
  48. A

    I How is static friction the centripetal force during a car turning?

    Hello, as you can see i am trying to understand conceptually how the tires during turning create a centripetal force. It was explained to me that as we turn the car tires, the tires similar to a ski or a wedge, now want to push the ground to the side and forward. If the ground was loose, this...
  49. M

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    Hello, I have a structure with 5 pivot point and those are provided with deep groove ball bearings (see sketch). Calculation for friction losses (deep grove ball bearing): Parameters: - Number of pivot points: 5 - Friction coefficient: 0.0010 - 0.0015 (Reference) Total friction in the...
  50. sam0916

    Engineering Angle of Wrap (Belt Friction)

    Attached is the picture of the belt. The angle of wrap seems to be >180 degrees.
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