▁syn onym s , ▁but ▁typically ▁they ▁are ▁measured ▁with ▁a ▁different ▁unit . ▁Angular ▁speed , ▁however , ▁tells ▁the ▁change ▁in ▁angle ▁per ▁time ▁unit , ▁which ▁is ▁measured ▁in ▁rad ians ▁per ▁second ▁in ▁the ▁SI ▁system . ▁Since ▁there ▁are ▁ 2 π ▁rad ians ▁per ▁cycle , ▁or ▁ 3 6 0 ▁degrees ▁per ▁cycle , ▁we ▁can ▁convert ▁angular ▁speed ▁to ▁rot ational ▁speed ▁by ▁ ▁and ▁ ▁where ▁▁ ▁is ▁rot ational ▁speed ▁in ▁cycles ▁per ▁second ▁▁ ▁is ▁angular ▁speed ▁in ▁rad ians ▁per ▁second ▁▁ ▁is ▁angular ▁speed ▁in ▁degrees ▁per ▁second ▁ ▁For ▁example , ▁a ▁ste pper ▁motor ▁might ▁turn ▁exactly ▁one ▁complete ▁revolution ▁each ▁second . ▁Its ▁angular ▁speed ▁is ▁ 3 6 0 ▁degrees ▁per ▁second ▁( 3 6 0 ° / s ), ▁or ▁ 2 π ▁rad ians ▁per ▁second ▁( 2 π ▁rad / s ), ▁while ▁the ▁rot ational ▁speed ▁is ▁ 6 0 ▁r pm . ▁ ▁Rot ational ▁speed ▁is ▁not ▁to ▁be ▁confused ▁with ▁tang ential ▁speed , ▁despite ▁some ▁relation ▁between ▁the ▁two ▁concepts . ▁Im agine ▁a ▁rot ating ▁mer ry - go - round . ▁ ▁No ▁matter ▁how ▁close ▁or ▁far ▁you ▁stand ▁from ▁the ▁axis ▁of ▁rotation , ▁your ▁rot ational ▁speed ▁will ▁remain ▁constant . ▁However , ▁your ▁tang ential ▁speed ▁does ▁not ▁remain ▁constant . ▁ ▁If ▁you ▁stand ▁two ▁meters ▁from ▁the ▁axis ▁of ▁rotation , ▁your ▁tang ential ▁speed ▁will ▁be ▁double ▁the ▁amount