▁A ▁is ▁▁ ▁If ▁the ▁potential ▁is ▁re defined ▁at ▁A ▁to ▁be ▁ ▁and ▁the ▁potential ▁at ▁B ▁to ▁be ▁, ▁where ▁ ▁is ▁a ▁constant ▁( i . e . ▁ ▁can ▁be ▁any ▁number , ▁positive ▁or ▁negative , ▁but ▁it ▁must ▁be ▁the ▁same ▁at ▁A ▁as ▁it ▁is ▁at ▁B ) ▁then ▁the ▁work ▁done ▁going ▁from ▁A ▁to ▁B ▁is ▁▁ ▁as ▁before . ▁ ▁In ▁practical ▁terms , ▁this ▁means ▁that ▁one ▁can ▁set ▁the ▁zero ▁of ▁ ▁and ▁ ▁anywhere ▁one ▁lik es . ▁One ▁may ▁set ▁it ▁to ▁be ▁zero ▁at ▁the ▁surface ▁of ▁the ▁Earth , ▁or ▁may ▁find ▁it ▁more ▁convenient ▁to ▁set ▁zero ▁at ▁infinity ▁( as ▁in ▁the ▁expressions ▁given ▁earlier ▁in ▁this ▁section ). ▁ ▁A ▁conserv ative ▁force ▁can ▁be ▁expressed ▁in ▁the ▁language ▁of ▁differential ▁geometry ▁as ▁a ▁closed ▁form . ▁As ▁E uclidean ▁space ▁is ▁contract ible , ▁its ▁de ▁R ham ▁coh om ology ▁van ishes , ▁so ▁every ▁closed ▁form ▁is ▁also ▁an ▁exact ▁form , ▁and ▁can ▁be ▁expressed ▁as ▁the ▁gradient ▁of ▁a ▁scalar ▁field . ▁This ▁gives ▁a ▁mathematical ▁just ification ▁of ▁the ▁fact ▁that ▁all ▁conserv ative ▁forces ▁are ▁grad ients ▁of ▁a ▁potential ▁field . ▁ ▁Notes ▁ ▁References ▁ ▁External ▁links ▁What ▁is ▁potential ▁energy ? ▁ ▁Category : Forms ▁of ▁energy ▁Category : G rav ity <0x0A> </s> ▁The ▁arch ery ▁compet itions ▁at ▁the ▁ 2 0 1 7 ▁S out heast ▁Asian ▁Games ▁in ▁K