Changes

A [[force]] resulting from the contact of two surfaces. This force opposes motion.<ref>Wile, Dr. Jay L. ''Exploring Creation With Physical Science''. Apologia Educational Ministries, Inc. 1999, 2000</ref>. For solid bodies, one can distinguish two types of friction:

'''Friction''' is a [[force]] resulting from the contact of two surfaces. This force opposes motion.<ref>Wile, Dr. Jay L. ''Exploring Creation With Physical Science''. Apologia Educational Ministries, Inc. 1999, 2000</ref>. For solid bodies, one can distinguish two types of friction:

;[[static friction]]

;[[Static friction]]

:the force that is needed for motion to start if the surfaces are initially at rest with respect to each other.

:the force that is needed for motion to start if the surfaces are initially at rest with respect to each other.

;[[Kinetic friction]]

;[[Kinetic friction]]