Relative density
A pycnometer (from Greek: πυκνός (puknos) meaning "dense"), also called pyknometer or specific gravity bottle, is a device used to determine the density of a liquid. A pycnometer is usually made of glass, with a close-fitting ground glass stopper with a capillary tube through it, so that air bubbles may escape from the apparatus. This device enables a liquid's density to be measured accurately by reference to an appropriate working fluid, such as water or mercury, using an analytical balance.
Flotation of flexible objects
Consider two plates of infinite width, thickness formula_2, and length formula_3 that are connected by a torsional spring with spring constant per unit width formula_4. Furthermore, let formula_5 be the angle between a plate and the horizontal, and formula_6 the from where the meniscus meets the plate to the horizontal. The distance from the undisturbed water line to the plate's outer edge is formula_7. The density of water is formula_8, the density of air is considered negligible, and the plate density, formula_9, shall be varied. All systems naturally assume a configuration that minimizes total energy. Thus, the goal of this analysis is to identify the configurations (i.e., values of formula_7 and formula_5) that result in a stable equilibrium for a given value of formula_9.