crack' the whip'
1. to demand obedience, hard work, or efficiency from others in a harsh or stern manner.
2. Also called snap the whip. a game in which players in a line, each holding the next, run, roller-skate, or ice-skate for a distance until the leader veers suddenly in a new direction, causing the rest of the line to swing around rapidly and the players at the end of the line to lose their balance or to let go of the other players.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.