What's only useful while broken ?

An egg.

Explanation:

From human perspective, you need to break the egg in order to use it. Therefore it's more useful broken. This example does exclude easter eggs that are for decoration, but you get the point.

something that's only useful while broken is an egg

answer: the four parts of the "australian ballot" 1. the ballot paper is printed at public expense. 2. the ballot paper lists all candidates by position, as well as any other propositions. 3. ballot papers are distributed only at the polling place. 4. ballot papers are filled out by the voter in private. (secret ballot).

voracity is the noun corresponding to the adjective voracious, which means (1) eager to consume a great amount of food, or (2) marked by an insatiable appetite. veracity is far more common than the rare voracity, so the latter is sometimes used in place of the former.