What is Friction ( contact force )Force that acts when two objects rub (contact)

each otherFriction comes from solid, air or water

http://phet.colorado.edu/sims/friction/friction_en.html ( Let us visit this website)

How does Friction affects motion?

Friction opposes movement

How does Friction affects motion?

Slows down

How does Friction affects motion?

Getting moving

How does Friction affects motion?

Getting moving

How does Friction affects motion?

Grip or stop

Factors affecting friction ( surface)http://www.bbc.co.uk/schools/scienceclips/ages/8_9/friction.shtml ( visit this website)

Smooth surface Rough surface

Lesser bump and hollows means lesser

frictioncan move the object continuously with little

force.

More bump and hollows means more friction

Can move the object slowly with greater force

Smooth surfaceThe smoother the surface the faster the object glides with little force

Rough surfaceObjects will move slowly with greater force on the rough surface.

Factors affecting frictionAir Resistance Example:Is the force that provide a backward

forceSize and shape are the

factors that affect air resistance. ( the

bigger the size and shape the more is the

air resistance)

http://www.youtube.com/watch?v=oTMLXBeQ40E

http://www.youtube.com/watch?NR=1&v=ur40O6nQHsw

Friction: Good and BadGood BadHold objectsStops objectAble to play ,run ,walk

etcGives energy

Shoes, slippers , tires and anything that are used for moving are worn out.

Machine become less efficient

Reduce speed Cause accidents Cause sparks

Ways of reducing frictionApplying wax or polishingUse rotating objectsStreamliningNew design shoes for the athletes