Drop (liquid)

[1] A simple way to form a drop is to allow liquid to flow slowly from the lower end of a vertical tube of small diameter.

Some substances that appear to be solid, can be shown to instead be extremely viscous liquids, because they form drops and display droplet behavior.

The mass m of the drop hanging from the end of the tube can be found by equating the force due to gravity (

) giving the formula where α is the angle of contact with the tube's front surface, and g is the acceleration due to gravity.

The limit of this formula, as α goes to 90°, gives the maximum weight of a pendant drop for a liquid with a given surface tension,

This relationship is the basis of a convenient method of measuring surface tension, commonly used in the petroleum industry.

The term droplet is a diminutive form of 'drop' – and as a guide is typically used for liquid particles of less than 500 μm diameter.

In spray application, droplets are usually described by their perceived size (i.e., diameter) whereas the dose (or number of infective particles in the case of biopesticides) is a function of their volume.

The major source of sound when a droplet hits a liquid surface is the resonance of excited bubbles trapped underwater.

These oscillating bubbles are responsible for most liquid sounds, such as running water or splashes, as they actually consist of many drop-liquid collisions.

The classic shape associated with a drop (with a pointy end in its upper side) comes from the observation of a droplet clinging to a surface.

[9] Larger drops tend to be flatter on the bottom part due to the pressure of the gas they move through.

[9] The largest recorded raindrop was 8.8 mm in diameter, located at the base of a cumulus congestus cloud in the vicinity of Kwajalein Atoll in July 1999.

[14] In medicine, this property is used to create droppers and IV infusion sets which have a standardized diameter, in such a way that 1 millilitre is equivalent to 20 drops.