Water Bottle Flipping Physics

TL;DR

This paper investigates the physics behind water bottle flipping, demonstrating how redistribution of water mass increases the moment of inertia, reduces angular velocity, and improves landing stability through experiments and analytical modeling.

Contribution

It provides an analytical model and experimental validation explaining how water redistribution affects the flip, offering insights for optimizing successful landings.

Findings

Angular velocity decreases significantly during flip

Water redistribution increases moment of inertia

Model helps optimize flip success

Abstract

The water bottle flipping challenge consists of spinning a bottle, partially filled with water, and making it land upright. It is quite a striking phenomenon, since at first sight it appears rather improbable that a tall rotating bottle could make such a stable landing. Here we analyze the physics behind the water bottle flip, based on experiments and an analytical model that can be used in the classroom. Our measurements show that the angular velocity of the bottle decreases dramatically, enabling a nearly vertical descent and a successful landing. The reduced rotation is due to an increase of the moment of inertia, caused by the in-flight redistribution of the water mass along the bottle. Experimental and analytical results are compared quantitatively, and we demonstrate how to optimize the chances for a successful landing.