What is a jump break billiards cue?

Answer 1

A jump break cue is a cue that billiard players use to break with and also the same cue breaks down into a jump cue. Traditionally, a break cue is a heavier cue that has a stiff shaft to transfer power from the player to the cue and ultimately to the racked balls on the other side of the table. There is a notion that a thinner shaft will give a "whip" action. this "whip action ismilliseconds after the hit on the cue ball, the shaft is temporally deformed and in another couple milliseconds, the shaft violently returns back to its original straight form. The violent return to its original form is the whip action.

The jump portion of the cue is the shaft and the front prong (front 12" of cue behind the shaft and before the handle of the cue) of the cue that separates from the rest of the cue.
Legal jumps in billiards are strikes on the upper half of the cue ball. The action of the cue ball is pressed down onto the table and as a reaction, the cue ball squirts in an upward motion leaving the table surface.

Jump cues need to be light in weight as to make contact with the cue ball and be off of the it so the milliseconds it takes for the cue ball to respond, it won't be restricted by a jump cue that is still in the way of the cue ball's jump.