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Topic: Static friction

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Rolling friction

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	Friction - MSN Encarta
		Friction, force that opposes the motion of an object when the object is in contact with another object or surface.
		Friction depends on this force because increasing the amount of force increases the amount of contact that the object has with the surface at the microscopic level.
		In this equation, F is the force of friction, µ is the coefficient of friction between the object and the surface, and N is the normal force.
	encarta.msn.com /encnet/refpages/RefArticle.aspx?refid=761569794 (1543 words)

	Force
		Frictional resistance to the relative motion of two solid objects is usually proportional to the force which presses the surfaces together as well as the roughness of the surfaces.
		Therefore two coefficients of friction are sometimes quoted for a given pair of surfaces - a coefficient of static friction and a coefficent of kinetic friction.
		Friction is typically characterized by a coefficient of friction which is the ratio of the frictional resistance force to the normal force which presses the surfaces together.
	hyperphysics.phy-astr.gsu.edu /hbase/frict.html (734 words)

	Friction
		It is that threshold of motion which is characterized by the coefficient of static friction.
		The coefficient of static friction is typically larger than the coefficient of kinetic friction.
		The coefficient is typically less than the coefficient of static friction, reflecting the common experience that it is easier to keep something in motion across a horizontal surface than to start it in motion from rest.
	hyperphysics.phy-astr.gsu.edu /hbase/frict2.html (713 words)

	Friction - Wikipedia, the free encyclopedia
		Friction is the force that opposes the relative motion or tendency of such motion of two surfaces in contact.
		Static friction is the same as the force being applied (because the body isn't moving).
		Fluid friction is the friction between a solid object as it moves through a liquid or a gas.
	en.wikipedia.org /wiki/Static_friction (1678 words)

	Friction
		Friction, which is worse in vacuum, has caused irreversible failures in many space instruments.
		The first practical application of friction dates from nearly a million years ago, when it was discovered that heat from friction could be used to light a fire.
		In a simple case of friction, if we apply a force parallel to the surface, there is no motion until we exceed a minimum force, see the figure.
	www.virginia.edu /ep/SurfaceScience/friction.html (855 words)

	How to measure friction?
		The coefficient of friction is found by the quotient of the friction load and the normal load, i.e.
		The moment at which the block begins to slide is the so called static coefficient of friction, the angle at which the block continues to slide with constant speed is the so called dynamic or kinetic coefficient of friction.
		To meaure the static coefficient of friction under conditions of high contact pressure the object may be clamped between two mating surfaces.
	www.tribology-abc.com /abc/friction.htm (360 words)

	Static and Kinetic Friction (Site not responding. Last check: 2007-10-14)
		There is a limit to the magnitude of static friction, so eventually you may be able to apply a force larger than the maximum static force, and the box will move.
		Both static and kinetic friction depend on the surfaces of the box and the floor, and on how hard the box and floor are pressed together.
		N, the slope of this graph is the coefficient of static friction
	www.yhc.edu /external/hramm/214Lab4.PwC12.Friction.F02.htm (1912 words)

	Static & Kinetic Friction
		The level of friction that different materials exhibit is measured by the coefficient of friction.
		The formula is µ = f / N, where µ is the coefficient of friction, f is the amount of force that resists motion, and N is the normal force.
		Another option is pumping the brake, which has the effect of alternating the use of kinetic and static friction as the wheels lock and unlock.
	ffden-2.phys.uaf.edu /211_fall2002.web.dir/Ben_Townsend/StaticandKineticFriction.htm (875 words)

	Friction -- from Eric Weisstein's World of Physics
		Friction is the resistive force acting between bodies that tends to oppose and damp out motion.
		Friction is usually distinguished as being either static friction (the frictional force opposing placing a body at rest into motion) and kinetic friction (the frictional force tending to slow a body in motion).
		The force due to kinetic friction is generally proportional to the applied force, so "a coefficient of kinetic fiction" is defined as the ratio of frictional force to the normal force on the body.
	scienceworld.wolfram.com /physics/Friction.html (132 words)

	Friction
		Friction is a force (measured in Newtons) acting along the surfaces of two objects in physical contact that impedes the relative motion of these objects (the motion of one with respect to the other).
		Static friction: the frictional force that opposes any attempt to move a stationary object along a surface.
		And so the coefficient of static friction is simply defined as the tangent of the critical angle (note that as the incline is raised higher and higher, the force due to gravity, what we call the weight, increases down the incline and the force pressing the block against the incline, F
	www2.ignatius.edu /faculty/decarlo/friction.htm (606 words)

	Resistive Force of Friction - Succeed in Physical Science
		The causes of sliding friction are surface roughness of the materials, molecular attraction or adhesion between the materials, and deformation resistance in the case of soft materials.
		Causes of fluid friction are turbulence effects from surface roughness and deformities, molecular attraction or adhesion between the materials, and deformation resistance of the fluid.
		Friction is a force that resist the motion of the object that is in contact with another object or material.
	www.school-for-champions.com /science/friction.htm (1418 words)

	Friction (Site not responding. Last check: 2007-10-14)
		Friction is the force between surfaces in contact that resists their relative tangential motion.
		Friction is largely independent of surface roughness (despite what you may have read in other textbooks).
		ABS ensures that the wheels retain their static frictional grip on the road, which allows for maneuvering while braking in an emergency.
	hypertextbook.com /physics/mechanics/friction (1169 words)

	Physics 2A Lab
		The force that opposes the sliding of the bodies is known as the friction force : the friction force is parallel to the contact surface and always directed against the applied force.
		is the coefficient of static friction and n is the normal force.
		The static frictional force is greater than the kinetic frictional force.
	tigre.ucr.edu /dipen/phy2a/friction.htm (374 words)

	The Force of Friction (Site not responding. Last check: 2007-10-14)
		Friction is also dependant on the amount of contact force pushing the two surfaces together (normal force).
		The maximum force of static friction is used because static friction has a whole range from zero newtons up to the maximum force of static friction.
		The coefficient of static friction is usually a little bit higher than coefficient of kinetic friction for the same two surfaces.
	regentsprep.org /Regents/physics/phys01/friction (600 words)

	Inline Grip, Friction And Skating Force-- Speedskating Santa Barbara
		Static friction is neither a power loss nor gain but does allow you to produce power when stroking.
		I assume that the coefficient of static friction applies in both static and rolling friction but because of the cycloidal motion they may well be different.
		Sliding friction is useful as an emergency measure (the hockey slide) but it is a power loss and is not usually involved in racing.
	home1.gte.net /pjbemail/GripFriction.html (1843 words)

	Static Friction
		Static friction is a force that is not well understood, but it is extremely important.
		Exert a gentle enough pull (force f) on the handle so that it doesn't slide, and that means that the force of static friction must be of equal magnitude in the opposite direction (force -f).
		is called the coefficient of static friction, and it is a constant for a given pair of surfaces.
	instruct.tri-c.edu /fgram/web/stafric.htm (251 words)

	Summary of Friction (Site not responding. Last check: 2007-10-14)
		The maximum force of static friction that exists between two surfaces is proportional to the normal force and mostly independent of area of contact.
		In general frictional forces are independent of the area of contact although this is an empirical observation not a theory.
		The reason that friction is nearly independent of surface area is if the "microscopic" area of contact of the brick to the table is independent of the orientation of the brick.
	zebu.uoregon.edu /1999/ph161/friction.html (508 words)

	Trials and Tribulations of Tribology
		He established a theory of dry friction (since called Coulomb friction) that predicts the maximum friction forces that are exerted on an object in contact with a dry surface before that object moves and becomes dynamic.
		The Coulomb static friction model states that the magnitude of the friction force is less than or equal to the normal force, N, multiplied by a constant coefficient of static friction, ms.
		What is interesting, and complicated, about static friction is the fact that the friction force increases to equal the applied force until this threshold has been reached.
	www.gamasutra.com /features/20000510/lander_pfv.htm (2318 words)

	Rolling Friction
		Static friction is where the velocity between the two objects is zero, but a frictional force is still present.
		It is also not static friction since the wheel is moving, though the point of contact is not; if there were no rolling friction, the wheel would continue forever on a perfectly level surface.
		Rolling friction is due mainly to the deformation of the wheel.
	www.newton.dep.anl.gov /askasci/phy00/phy00698.htm (872 words)

	Rolling Friction - Succeed in Physical Science
		This frictional force is typically a combination of several friction forces and is at the point of contact with the ground or other surface.
		In sliding friction, this surface roughness is the reason for the static and kinetic resistance to motion.
		This frictional force is typically a combination of several friction forces at the point of contact with the ground.
	www.school-for-champions.com /science/frictionrolling.htm (1454 words)

	Sliding Friction, Laboratory Exercise
		such that the frictional force is smaller after the motion has started than it is when the two objects are both at rest.
		We see the interesting result that the coefficient of friction can be measured in terms of the angle, and with no dependence upon the size and mass of the block itself.
		The static frictional forces are always larger than the kinetic frictional forces and not so reproducible, experimentally.
	www.pa.uky.edu /~phy211/Friction_book.html (356 words)

	Friction
		A third type of friction, rolling friction, is a special case of static friction and will be discussed later.
		And so the coefficient of static friction is simply defined as the tangent of the critical angle.
		If the tires skid, for instance if the wheels lock on braking, the sliding friction is less than static friction and so the car will take a longer time to slow down.
	www2.ignatius.edu /faculty/decarlo/friction3.htm (557 words)

	Friction (Site not responding. Last check: 2007-10-14)
		Friction is the resistance to motion of an object that slides or attempts to slide over a surface.
		The coefficient of friction is used to calculate the F
		It is a ratio of the magnitude of the force of friction, F
	www.rhhs.ca /new_page_80.htm (281 words)

	Physics 128 Lecture: Friction and Free-body Diagrams (Site not responding. Last check: 2007-10-14)
		The direction of the static frictional force is along the contact surface and opposite in direction of any applied force.
		The direction of the kinetic frictional force is opposite the direction of motion of the object it acts on.
		While the locomotive's force on the car is equal and opposite to the car's force on the locomotive the frictional force between the locomotive and the track is greater than the frictional force between the coal car and the track allowing them to move forward.
	www.cord.edu /dept/physics/p128/lecture99_12.html (1387 words)

	Coefficient of friction - Wikipedia, the free encyclopedia
		The force of friction depends on the normal force, which is the force pressing the two surfaces together.
		The coefficient of friction is a measure of the slipperiness between two surfaces: the larger the coefficient of friction, the less slippery the surfaces.
		The friction force is electromagnetic in origin: atoms of one surface "stick" to atoms of the other briefly before snapping apart, causing atomic vibrations, and thus transforming the work needed to maintain the sliding into heat.
	en.wikipedia.org /wiki/Coefficient_of_friction (546 words)

	Static Friction (Site not responding. Last check: 2007-10-14)
		To increase the friction force, you can increase the normal force; that is you "squeeze harder" on the bill.
		The static friction force adjusts to "keep things static." Because of this it is not possible to calculate the static friciton force if all we know is the normal force(s).
		The only static friction force that can be predicted is the maximum static friction force; the force at which the dollar bill just begins to slip.
	members.aol.com /jwdooley/eqns/FORCES/SURFACE/STATIC/STATIC.HTM (248 words)

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