"A popular party trick is to ﬁll a glass bottle with water and hit the top of the bottle with an open hand, causing the bottom of the bottle to break open. We investigate the source of the catastrophic cracking through the use of high-speed video and an accelerometer attached to the bottom of a glass bottle.
Upon closer inspection, it is obvious that the acceleration caused by hitting the top of the bottle is followed by the formation of bubbles near the bottom. The nearly instantaneous acceleration creates an area of low pressure on the bottom of the bottle where cavitation bubbles form. Moments later, the cavitation bubbles collapse at roughly 10 times the speed of formation, causing the bottle to break. The accelerometer data shows that the bottle is broken after the bubbles collapse and that the magnitude of the bubble collapse is greater than the initial impact. The ﬂuid dynamics video highlights that this trick will not work if the bottle is empty nor if it is ﬁlled with a carbonated ﬂuid because the vapor bubbles ﬁll with the CO2 dissolved in the liquid, preventing the bubbles from collapsing.
A modiﬁed cavitation number, including the acceleration of the ﬂuid (a), vapor pressure (Pv), and depth of the ﬂuid column (h), is derived to determine when cavity inception occurs such that Ca =(Patm − Pv)/(ρh(a − g)). Through experimentation, visible cavitation bubbles form when Ca ≤ 0.5. The experiments, based on the modiﬁed cavitation number, reveal that the easiest way to break a glass bottle with your bare hands is to ﬁll it with a non-carbonated, high vapor pressure ﬂuid, and strike it hard."