What is the difference between contact force and forces that act through a force field?

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sciftw | High School Teacher | (Level 1) Educator Emeritus

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Contact forces are forces that require the actual contact (touching) of two pieces of matter.  There are a variety of contact forces.  A very common one is friction.  Anytime that two surfaces are in contact with one another, there is friction between the two surfaces.  The surfaces don't have to be solid either.  A skydiver still experiences friction as he "slides" through the air.  Specifically that is fluid friction.  Other types of contact forces are elastic, spring, and tension forces.  

A field force is a force that works at a distance.  No touching is required.  Gravity is a good example of a field force, because it works whether or not an object is touching something or touching nothing at all.  Two other forces of this type are electrical force and magnetic force.