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Name: Praneeth
Status: student
Age: 11
Location: N/A
Country: N/A
Date: 2001


Question:
Why are raindrops always round?


Replies:
Raindrops are not always round. They are "tear-shaped" blunt end down due to air resistance.

Vince Calder


Praneeth,

Molecules that are alike tend to stick together. When drops of water are in free-fall -- as is the case with raindrops -- the molecules' mutual attraction for each other pull the water drop into the shape of a tiny sphere because that shape has the smallest surface area that the piece (drop) of water can take on itself.

This is true for any liquid. Tiny drops in free-fall are always round

Regards,
ProfHoff 362


Praneeth, A drop is round, if it is not falling through the air (in other words, if it is suspended in the air or in another fluid). When falling through the air, the bottom of the drop is flattened somewhat by the air that it is moving through.

However, drops are round because of a property of the physics of liquids called surface tension. A round shape is the easiest to maintain. If you start a mass of liquid out with another shape (like a cube), it will want to round out any corners and become a drop, or if in a container, it will want to take the shape of the container.

David R. Cook
Atmospheric Research Section
Environmental Research Division
Argonne National Laboratory


Dear Praneeth-

Under undisturbed conditions, raindrops would be round, caused by the surface tension of the droplet, but their motion and environment causes changes to their shape. Raindrops form from very small spherical water droplets, and begin to fall to earth due to gravity. This movement causes the raindrops to be more oval-shaped on the bottom, and more flat on top, similar to an English muffin or biscuit. Air currents can distort the shape even further, and sometimes cause the drops to break up into smaller drops.

Wendell Bechtold, meteorologist
Forecaster, National Weather Service
Weather Forecast Office, St. Louis, MO


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