In this case the force of friction between the bottom disc and the one in contact with it acts for too short a time to cause any appreciable movement of the discs above.
(the force of friction between the bottom disc and the one in contact with it; acts; T:for too short a time; L:In this case)
the force of friction between the bottom disc and the one in contact with it
acts
T:for too short a time L:In this case