Friction

Friction is a good thing:

Just think of walking on a wet marble floor or an icy pavement with new leather soled
shoes: you might slip over! Worse still, if the tyres on your car are worn out and the
road is wet and slippery, you will probably skid the car and have an accident. Both your
shoes and the car’s tyres need good grip so their surfaces are rough. This increases the
friction between them and the ground.

Friction is also very important for your car’s brakes to work properly. When you put
you foot on the brake pedal, some rough pads are squeezed tight against the brake discs.
This friction slows the car down. If oil gets on the discs, the brakes will not work so
well.

Friction is a bad thing:

Friction inside a car engine and inside the wheel axles will slow a car down and wear
out the metal. To prevent this we put oil or even grease in them. This makes their
surfaces more slippery and so reduces friction.

I hope that you will be able to remember most of the facts on this page, but you must
memorise the definition of a friction. Write it on a small index card. Put the red
words on one side of the card and the blue ones on the other. Add the card  to your
revision pack.

Friction is the force between to surfaces
rubbing together. It is high if the surfaces are dry and rough and it is low if the
surfaces are smooth and wet.

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