what are the conditions and causes of friction...???x?

Answer 1

Friction can occur when two materials slide (kinetic friction) or try to slide (static friction) along each other. The surface features (depressions and protrusions) can be rough and hard (two sheets of sandpaper) in which case either the surfaces must separate slightly or the features must break. The features may be one rough and hard and the other soft (tire on pavement) in which case the soft surface deforms into the features on the hard surface, and must deform further to slide. Soft-to-soft friction is also possible. Not all friction requires roughness. Cold-welding of very clean smooth metal surfaces can occur due to intermolecular forces. (Of course hot-welding is also possible in the presence of dry metallic friction, e.g., a bearing running dry.) Friction force is usually modelled as proportional to the force pressing the surfaces together. Interestingly, friction can be difficult to model in a time-domain simulation, with spurious chatter often being the result. However, chatter and creaking are often a natural occurrence in systems that have friction and flexure. One mode of chatter is due to a "stick-slip" effect when the static friction is greater than the kinetic friction. See the ref. for more theory of friction.

Answer 2

Far too much punctuation.

Anyways; the pressure with which an object is pushed or pulled towards the center of gravity (i.e. weight of the object, gravity, air pressure), the textures of the two surfaces contacting (see coefficient of friction), whether or not the object is moving... that's about it

Answer 3

Load, Temperature, Lubrication

Answer 4

how hard you push against the ground
how rough the ground is.

Answer 5

It's her fault I tell ya! Change me? Never!