▁vis cos ity ▁of ▁non - New ton ian ▁flu ids ▁is ▁dependent ▁on ▁she ar ▁rate ▁or ▁she ar ▁rate ▁history . ▁In ▁a ▁non - New ton ian ▁fluid , ▁the ▁relation ▁between ▁the ▁she ar ▁stress ▁and ▁the ▁she ar ▁rate ▁is ▁different ▁and ▁can ▁even ▁be ▁time - dependent ▁( Time ▁Dep endent ▁Vis cos ity ). ▁Therefore , ▁a ▁constant ▁coefficient ▁of ▁vis cos ity ▁cannot ▁be ▁defined . ▁ ▁Non - New ton ian ▁flu ids ▁change ▁their ▁vis cos ity ▁or ▁flow ▁behavior ▁under ▁stress . ▁If ▁a ▁force ▁is ▁applied ▁to ▁such ▁flu ids , ▁the ▁sudden ▁application ▁of ▁stress ▁can ▁cause ▁them ▁to ▁get ▁th icker ▁and ▁act ▁like ▁a ▁solid , ▁or ▁in ▁some ▁cases , ▁it ▁results ▁in ▁the ▁opposite ▁behavior ▁and ▁they ▁may ▁get ▁run nier ▁than ▁they ▁were ▁before . ▁Rem oval ▁of ▁the ▁stress ▁causes ▁them ▁to ▁return ▁to ▁their ▁earlier ▁state . ▁Not ▁all ▁non - New ton ian ▁Fl u ids ▁behave ▁in ▁the ▁same ▁way ▁when ▁stress ▁is ▁applied ▁– ▁some ▁become ▁more ▁solid , ▁others ▁more ▁fluid . ▁Some ▁non - New ton ian ▁flu ids ▁react ▁as ▁a ▁result ▁of ▁the ▁amount ▁of ▁stress ▁applied , ▁while ▁others ▁react ▁as ▁a ▁result ▁of ▁the ▁length ▁of ▁time ▁that ▁stress ▁is ▁applied . ▁The ▁generalized ▁power ▁law ▁for ▁all ▁flu ids ▁can ▁be ▁written ▁as : ▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁ ▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁ ▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁ ▁▁▁▁▁▁ ▁Where ▁ ▁K ▁= ▁flow ▁consist ency ▁index ▁▁▁▁▁▁▁▁▁▁▁▁▁▁ ▁n ▁= ▁Fl uid ▁behavior ▁index