Friction is a that tries to prevent objects from passing smoothly over each other.
It occurs where two objects are in .
Friction can prevent a car engine from moving .
It can also cause the moving parts to up.
That's why cars use such as oil, to help keep the parts moving freely.
To reduce friction, wheels are often mounted on ball , or oil is used to make moving parts more .
Friction can also be quite .
It allows shoes and tyres to the ground.
It is also useful in systems of cars and other forms of transport.