▁of ▁random ▁mot ions ▁of ▁particles ▁and ▁the ▁potential ▁energy ▁of ▁their ▁configuration . ▁ ▁Forces ▁deriv able ▁from ▁a ▁potential ▁are ▁also ▁called ▁conserv ative ▁forces . ▁ ▁The ▁work ▁done ▁by ▁a ▁conserv ative ▁force ▁is ▁ ▁where ▁ ▁is ▁the ▁change ▁in ▁the ▁potential ▁energy ▁associated ▁with ▁the ▁force . ▁The ▁negative ▁sign ▁provides ▁the ▁convention ▁that ▁work ▁done ▁against ▁a ▁force ▁field ▁increases ▁potential ▁energy , ▁while ▁work ▁done ▁by ▁the ▁force ▁field ▁decre ases ▁potential ▁energy . ▁ ▁Common ▁not ations ▁for ▁potential ▁energy ▁are ▁P E , ▁U , ▁V , ▁and ▁Ep . ▁ ▁Pot ential ▁energy ▁is ▁the ▁energy ▁by ▁virtue ▁of ▁an ▁object ' s ▁position ▁relative ▁to ▁other ▁objects . ▁Pot ential ▁energy ▁is ▁often ▁associated ▁with ▁rest oring ▁forces ▁such ▁as ▁a ▁spring ▁or ▁the ▁force ▁of ▁gravity . ▁The ▁action ▁of ▁stretch ing ▁a ▁spring ▁or ▁lif ting ▁a ▁mass ▁is ▁performed ▁by ▁an ▁external ▁force ▁that ▁works ▁against ▁the ▁force ▁field ▁of ▁the ▁potential . ▁ ▁This ▁work ▁is ▁stored ▁in ▁the ▁force ▁field , ▁which ▁is ▁said ▁to ▁be ▁stored ▁as ▁potential ▁energy . ▁ ▁If ▁the ▁external ▁force ▁is ▁removed ▁the ▁force ▁field ▁acts ▁on ▁the ▁body ▁to ▁perform ▁the ▁work ▁as ▁it ▁moves ▁the ▁body ▁back ▁to ▁the ▁initial ▁position , ▁reducing ▁the ▁stretch ▁of ▁the ▁spring ▁or ▁causing ▁a ▁body ▁to ▁fall . ▁ ▁Consider ▁a ▁ball ▁whose ▁mass ▁is ▁m ▁and ▁whose ▁height ▁is ▁h . ▁The ▁acceleration ▁g ▁of ▁free ▁fall ▁is ▁approximately ▁constant