Contact force

Block on a ramp and corresponding free body diagram of the block showing the contact force from the ramp onto the bottom of the block and separated into two components, a normal force N and a friction force f, along with the body force of gravity mg acting at the center of mass.

A contact force is any force that occurs as a result of two objects making contact with each other.[1] Contact forces are very common and are responsible for most visible interactions between macroscopic collections of matter. Pushing a car or kicking a ball are some of the everyday examples where contact forces are at work. In the first case the force is continuously applied to the car by a person, while in the second case the force is delivered in a short impulse.

Contact forces are often decomposed into orthogonal components, one perpendicular to the surface(s) in contact called the normal force, and one parallel to the surface(s) in contact, called the friction force.[1]

Not all forces are contact forces; for example, the weight of an object is the force between the object and the Earth, even though the two do not need to make contact. Gravitational forces, electrical forces and magnetic forces are body forces and can exist without contact occurring.

  1. ^ a b Plesha, Gray, and Costanzo (2010). Engineering Mechanics – Statics. McGraw-Hill. pp. 8-9.{{cite book}}: CS1 maint: multiple names: authors list (link)