What is a contact force?
Contact force - force between two objects (or an object and a surface) that are in contact with each other.

A contact force exists when an object touches something, which causes it to exert a force on it. Everytime you touch something or push/pull something, you exert a contact force. Ex. When you slide your text book to the side of your desk or when you hold your book, a contact force is taking place. A textbook sitting on a table has a contact force from the table exerted on it.

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This tow truck is exerting a contact force with the broken down car and the road. Also, the broken down car is exerting a contact force on the tow truck and the road as well. However, there are many other contact forces in this photo as well. Can you name some of them?

http://www.myphysicslab.com/contact.html

There are many types of contact forces including: frictional force, tension force, normal force, air resistance force, applied force and spring force.

Friction force - force exerted by a suface as an object moves across or makes an effort to move across it. Ex. the type of force exerted by the car tires driving on the road in the earlier picture.

Tension force - force of pull supplied by strings, ropes or chains. Ex. the type of contact force exerted by the cable on the broken down car in the earlier picture.

Normal force - unpreventable force that is perpendicular to the surface of contact. Ex. the contact force exerted by the surface of a floor or wall, preventing an object from entering the floor or wall.

Air resistance - friction between an object and the air. All matter is made from atoms and/or molecules. The air is no exception. When something moves through the air, it bumps into the atoms and molecules. Ex. the force of the front tires of the broken down car on the air in the earlier picture.

Applied force - force that is applied to an object by a person or another object. Ex. the force exerted by a person pushing a desk across a room.

Spring force - force exerted by a compressed or stretched spring upon any object that is attached to it. Ex. if someone lays on a mattress, some of the force is absorbed by the springs that are trying to resist the force so they won't completely compress.

In short...FORCES ARE EVERYWHERE!!! :)

By: Tawnie DeJong and Tomilyn Trask