FRICTION Any force that resists motion It involves

FRICTION

• Any force that resists motion • It involves objects that are in contact with each other. • This is the force that keeps an object from sliding down and incline plane.

Friction • Friction is a force that resists the motion of two surfaces that are touching. • When a moving object comes in contact with another object, friction is the opposing force that slows or stops the moving object.

• Some scientists believe that friction is caused by uneven surfaces of the touching objects – when rubbed together resistance is offered. • Experiments have shown that tiny particles are actually torn from one surface and imbedded in the other. • If two surfaces were carefully polished, there is a limit to the amount by which friction may be reduced. If made too smooth, the friction between them actually increases.

Types of Friction • Static. . prevents objects sliding • *Sliding. . . resists objects while they are moving • *Fluid…air or water

Examples of Friction • • Tires on the road Walking/Running Nails into wood Sled on hill

• Without friction, an object would continue to move at constant speed forever. • The strength of the force of friction depends on the type of surfaces and how hard the surfaces push together. • Rough surfaces produce greater friction than smooth surfaces.

Principles of Friction • Friction acts parallel to the surface that are in contact. • The direction that friction acts is OPPOSITE the direction of the motion (or intended motion). Fnormal Ffriction(k) Fapplied Fweight

Sliding Friction • A resistance to movement that is created when two things rub together.

Fluid Friction • The force that tries to slow objects down when they move through a liquid or a gas. It's also known as "drag", or "air resistance". • All gases and liquids are fluids. • An airplane and a swimmer both experience fluid friction.

Ø Static Friction – the frictional force present just before motion begins. Starting Friction is when Static Friction is at is maximum. Ø Kinetic Friction – the frictional force present with motion v. Note: Static Friction is usually higher than Kinetic Friction