Coulomb model of friction - Revision history

Vipul at 12:39, 24 August 2011

2011-08-24T12:39:47Z

← Older revision		Revision as of 12:39, 24 August 2011
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	\| [[Coulomb's law of friction]] \|\| magnitude of kinetic friction is independent of speed of slippage \|\| the Coulomb model for kinetic friction only takes into account the normal force and the ''direction'' of slippage, not the speed.		\| [[Coulomb's law of friction]] \|\| magnitude of kinetic friction is independent of speed of slippage \|\| the Coulomb model for kinetic friction only takes into account the normal force and the ''direction'' of slippage, not the speed.
	\|}		\|}

			==Case of sliding-cum-rotation==

			If one of the surfaces of contact is ''also'' undergoing rotational motion, then the relevant ''slipping'' is ''not'' the relative motion of the bodies but the relative motion of the ''surfaces'', which takes into account both the sliding and the rotation.

			A special case is the case of [[rolling]], which satisfies the [[no slip condition]]: there is no slipping at the surface of contact. This happens because the relative translational speed at the point of contact cancels the rotational speed at the point of contact.

			Thus, we note that:

			* In the case of rolling, where the no slip condition is satisfied, we apply the model for static friction. In particular, the friction force is bounded from above in magnitude by <math>\mu_sN</math>, but need not equal <math>\mu_sN</math>. The direction is determined by looking at the force and torque equations and seeing what makes sense.
			* In any case ''other'' than rolling, we have kinetic friction, so the model for kinetic friction applies. The magnitude of friction force is <math>\mu_kN</math>, and its direction is opposite the direction of relative slipping of the surfaces, which is determined by combining the translational motion of the bodies and the rotational motion at the region of contact.

Vipul: /* Definition */

2011-08-13T01:05:34Z

Definition

← Older revision		Revision as of 01:05, 13 August 2011
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	The '''Coulomb model of friction''', or the '''Amonton-Coulomb model of friction''', or '''Coulomb friction''', refers to a simple model of dry [[friction]] that is fairly accurate empirically. Specifically, it is a model that helps predict the direction and magnitude of the friction force between two bodies with dry surfaces in contact.		The '''Coulomb model of friction''', or the '''Amonton-Coulomb model of friction''', or '''Coulomb friction''', refers to a simple model of dry [[friction]] that is fairly accurate empirically. Specifically, it is a model that helps predict the direction and magnitude of the friction force between two bodies with dry surfaces in contact.

			{{quotation\|For more on how to ''apply'' this model of friction to mechanics scenarios, see [[applying the Coulomb model of friction]].}}

	==Model for static friction==		==Model for static friction==

Vipul: /* Definition */

2010-08-14T16:47:42Z

Definition

← Older revision		Revision as of 16:47, 14 August 2010
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	==Definition==		==Definition==

	The '''Coulomb model of friction''', or the '''~~Amoton~~-Coulomb model of friction''', or '''Coulomb friction''', refers to a simple model of dry [[friction]] that is fairly accurate empirically. Specifically, it is a model that helps predict the direction and magnitude of the friction force between two bodies with dry surfaces in contact.		The '''Coulomb model of friction''', or the '''Amonton-Coulomb model of friction''', or '''Coulomb friction''', refers to a simple model of dry [[friction]] that is fairly accurate empirically. Specifically, it is a model that helps predict the direction and magnitude of the friction force between two bodies with dry surfaces in contact.

	==Model for static friction==		==Model for static friction==

Vipul at 16:14, 14 August 2010

2010-08-14T16:14:27Z

← Older revision		Revision as of 16:14, 14 August 2010
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	==Definition==		==Definition==

	The '''Coulomb model of friction''', or '''Coulomb friction''', refers to a simple model of dry [[friction]] that is fairly accurate empirically. Specifically, it is a model that helps predict the direction and magnitude of the friction force between two bodies with dry surfaces in contact.		The '''Coulomb model of friction''', or the '''Amoton-Coulomb model of friction''', or '''Coulomb friction''', refers to a simple model of dry [[friction]] that is fairly accurate empirically. Specifically, it is a model that helps predict the direction and magnitude of the friction force between two bodies with dry surfaces in contact.

	==Model for static friction==		==Model for static friction==

Vipul at 22:02, 15 January 2010

2010-01-15T22:02:57Z

← Older revision		Revision as of 22:02, 15 January 2010
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	The proportionality with normal force, and the fact that this constant of proportionality is dependent on the nature of the surfaces in contact, is termed [[Amonton's second law of friction]]. The fact that the magnitude of area of contact plays no role is termed [[Amonton's first law of friction]]. The fact that the magnitude of friction force is independent of the speed of slipping is termed [[Coulomb's law of friction]].		The proportionality with normal force, and the fact that this constant of proportionality is dependent on the nature of the surfaces in contact, is termed [[Amonton's second law of friction]]. The fact that the magnitude of area of contact plays no role is termed [[Amonton's first law of friction]]. The fact that the magnitude of friction force is independent of the speed of slipping is termed [[Coulomb's law of friction]].

			==Related facts==

			{\| class="sortable" border="1"
			! Name !! Statement !! How it fits into the Coulomb model
			\|-
			\| [[Amonton's first law of friction]] \|\| magnitude of friction force is independent of contact area \|\| the Coulomb model for static friction as well as kinetic friction does not use the contact area either directly or indirectly.
			\|-
			\| [[Amonton's second law of friction]] \|\| magnitude of friction force is proportional to magnitude of normal force \|\| the Coulomb model predicts that in the static case, this is true for the ''limiting'' value of frictional force, with the constant of proportionality being the [[limiting coefficient of static friction]], while in the kinetic case, it is directly true, with the constant of proportionality being the [[coefficient of kinetic friction]].
			\|-
			\| [[Coulomb's law of friction]] \|\| magnitude of kinetic friction is independent of speed of slippage \|\| the Coulomb model for kinetic friction only takes into account the normal force and the ''direction'' of slippage, not the speed.
			\|}

Vipul at 15:47, 22 November 2009

2009-11-22T15:47:57Z

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			{{constitutive relation}}

	==Definition==		==Definition==

Vipul at 12:44, 24 June 2009

2009-06-24T12:44:09Z

← Older revision		Revision as of 12:44, 24 June 2009
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	The '''Coulomb model of friction''', or '''Coulomb friction''', refers to a simple model of dry [[friction]] that is fairly accurate empirically. Specifically, it is a model that helps predict the direction and magnitude of the friction force between two bodies with dry surfaces in contact.		The '''Coulomb model of friction''', or '''Coulomb friction''', refers to a simple model of dry [[friction]] that is fairly accurate empirically. Specifically, it is a model that helps predict the direction and magnitude of the friction force between two bodies with dry surfaces in contact.

			==Model for static friction==

			{{further\|[[Static friction]]}}

			Static friction occurs when there is no slipping between the two surfaces of contact. This can occur both when the two bodies are in rest relative to each other, and when the surfaces are rolling against each other.

			There exists a constant <math>\mu_s</math>, termed the [[limiting coefficient of static friction]], dependent on the nature of the two surfaces in contact, such that the static friction is determined by the following rules:

			* Static friction is equal in magnitude and opposite in direction to the net external force acting along the plane of contact that is causing a tendency for the surfaces to slip against each other. In other words, it acts to precisely cancel out the external force that would otherwise have caused slipping, thus producing no slipping.
			* The maximum value of static friction that can be experienced through the surface of contact equals <math>\mu_s N</math>, where <math>\mu_s</math> is the limiting coefficient of static friction and <math>N</math> is the [[normal force]]. In the limiting case, the two surfaces are said to ''just start slipping against each other''.

			The proportionality with normal force, and the fact that this constant of proportionality is dependent on the nature of the surfaces in contact, is termed [[Amonton's second law of friction]]. The fact that the magnitude of area of contact plays no role is termed [[Amonton's first law of friction]].

			==Model for kinetic friction==

			{{further\|[[Kinetic friction]]}}

			Kinetic friction, or dynamic friction, occurs when there is slipping between the two surfaces of contact. There exists a constant <math>\mu_k</math>, termed the [[coefficient of kinetic friction]], dependent on the nature of the two surfaces in contact, such that, for sufficiently small speeds of slipping:

			* Kinetic friction is opposite in direction to the direction of actual slipping. Its direction does not depend on the direction of other external forces.
			* The magnitude of kinetic friction is <math>\mu_kN</math>, where <math>\mu_k</math> is the coefficient of kinetic friction, and <math>N</math> is the [[normal force]] between the bodies.

			<math>\mu_k</math> for a given pair of surfaces is typically somewhat less than <math>\mu_s</math>, indicating that once two bodies start slipping against each other, it is easier for them to continue slipping.

			The proportionality with normal force, and the fact that this constant of proportionality is dependent on the nature of the surfaces in contact, is termed [[Amonton's second law of friction]]. The fact that the magnitude of area of contact plays no role is termed [[Amonton's first law of friction]]. The fact that the magnitude of friction force is independent of the speed of slipping is termed [[Coulomb's law of friction]].

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2009-06-24T12:16:02Z

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==Definition==

The '''Coulomb model of friction''', or '''Coulomb friction''', refers to a simple model of dry [[friction]] that is fairly accurate empirically. Specifically, it is a model that helps predict the direction and magnitude of the friction force between two bodies with dry surfaces in contact.