Chapter 5 Matter In Chapter 5 Matter In MotionMotion

Section 3 – Friction: A Force Section 3 – Friction: A Force That Opposes MotionThat Opposes Motion

p. 128 - 133p. 128 - 133

IMPORTANT DEFINITIONIMPORTANT DEFINITION►Friction – a Friction – a force that opposes motion force that opposes motion

between two surfaces that are between two surfaces that are touchingtouching

The amount of friction between two The amount of friction between two surfaces depends on:surfaces depends on:1. 1. the roughness of the two the roughness of the two surfacessurfaces. Rougher surfaces create . Rougher surfaces create more friction.more friction.2. 2. the forces that are pushing the the forces that are pushing the two surfaces togethertwo surfaces together. Greater . Greater force creates more friction.force creates more friction.

TYPES OF FRICTION TYPES OF FRICTION ►Sliding Kinetic Sliding Kinetic

Friction – Friction – the the type of friction type of friction produced when produced when two solid two solid objects slide objects slide over one over one anotheranother..

TYPES OF FRICTIONTYPES OF FRICTION►Rolling Kinetic Rolling Kinetic

Friction – Friction – the the type of friction type of friction that occurs that occurs when an object when an object rolls over a rolls over a surfacesurface

TYPES OF FRICTIONTYPES OF FRICTION►Fluid Kinetic Fluid Kinetic

Friction – Friction – the the type of friction type of friction that opposes that opposes motion when an motion when an object moves object moves through a fluid through a fluid (liquid or gas)(liquid or gas)

TYPES OF FRICTIONTYPES OF FRICTION►Static Friction – Static Friction –

this happens when a this happens when a force is applied to an force is applied to an object but the object object but the object does not movedoes not move..

► Static friction Static friction disappears as soon as disappears as soon as the object starts to the object starts to move.move.

HARMFUL OR HELPFUL?HARMFUL OR HELPFUL?

WAYS TO REDUCE FRICTIONWAYS TO REDUCE FRICTION►Use a lubricant. A lubricant is Use a lubricant. A lubricant is applied to applied to

surfaces to decrease the amount of friction surfaces to decrease the amount of friction between them.between them.

►Switch from Switch from sliding kinetic friction to rolling sliding kinetic friction to rolling kinetic frictionkinetic friction

►Smooth surfaces that rub togetherSmooth surfaces that rub together

WAYS TO INCREASE WAYS TO INCREASE FRICTIONFRICTION

►Make surfaces that rub together Make surfaces that rub together rougherrougher i.e. putting sand on icy roadsi.e. putting sand on icy roads

► Increase the force pushing the Increase the force pushing the surfaces togethersurfaces together

FrictionFriction► Friction exists throughout the universeFriction exists throughout the universe► It can be reduced but not eliminatedIt can be reduced but not eliminated► The closest frictionless environment would The closest frictionless environment would

be space.be space.► Space is a vacuum so there is no air Space is a vacuum so there is no air

resistance as long as there is no major resistance as long as there is no major gravitational force there is no natural gravitational force there is no natural pressurepressure……but if an object comes in contact but if an object comes in contact with another object there is friction with another object there is friction