InВо [[physicsФизика|физиката]], a '''force''' is any interaction that, when unopposed, will change the [[motion (physics)|motion]] of an [[Physical body|object]].<ref>{{cite web|last1=Nave|first1=C. R.|title=Force|url=http://hyperphysics.phy-astr.gsu.edu/hbase/force.html|website=Hyperphysics|publisher=Dept. of Physics and Astronomy, Georgia State University|accessdate=15 August 2014|year=2014}}</ref> In other words, a force can cause an object with [[mass]] to change its [[velocity]] (which includes to begin moving from a [[Newton's first law|state of rest]]), i.e., to [[accelerate]]. Force can also be described by intuitive concepts such as a push or a pull. A force has both [[Euclidean vector#Length|magnitude]] and [[Direction (geometry, geography)|direction]], making it a [[Vector (geometric)|vector]] quantity. It is measured in the [[SI unit]] of [[newton (unit)|newtons]] and represented by the symbol '''F'''.
The original form of [[Newton's second law]] states that the net force acting upon an object is equal to the [[time derivative|rate]] at which its [[momentum]] changes with time. If the mass of the object is constant, this law implies that the [[acceleration]] of an object is directly proportional to the net force acting on the object, is in the direction of the net force, and is inversely proportional to the [[mass]] of the object
