what is surface area and why rain drops are spherical?

Answer 1

Water drops are stable thanks to the high surface tension of water. This can be seen when small quantities of water are put onto a nonsoluble surface such as glass: the water stays together as drops. This property is important for life. For example, when water is carried through xylem up stems in plants the strong intermolecular attractions hold the water column together. Strong cohesive properties hold the water column together, and strong adhesive properties stick the water to the xylem, and prevent tension rupture caused by transpiration pull. Other liquids with lower surface tension would have a higher tendency to "rip", forming vacuum or air pockets and rendering the xylem water transport inoperative.

Answer 2

When no force acts on a liquid, the shape of liquid is spherical.
When rain drops fall, the drag force of air exactly counters the gravitational force.
Since the net force on the rain drop is zero, it is spherical.

Surface area is the measure of the material required to create a 3D figure.
Suppose you want to create a cube 3m in length.
You need 6 walls each of which has as area = 3*3 sq.m = 9 sq.m
Total surface area = 6*9 sq.m = 54 sq.m

Answer 3

One must use Calculus to find the surface area of a rain drop. It is not a perfect sphere. It maintains a "tail" on the trailing side. This is due to the fact that water is liquid and is able to modify its shape. It forms into the most aerodynamic shape on earth.

Answer 4

Falling raindrops are often depicted in cartoons or anime as "teardrop-shaped" — round at the bottom and narrowing towards the top — but this is incorrect. Only drops of water dripping from some sources are tear-shaped at the moment of formation. Small raindrops are nearly spherical. Larger ones become increasingly flattened on the bottom, like hamburger buns; very large ones are shaped like parachutes. [1] The shape of raindrops was studied by Philipp Lenard in 1898. He found that small raindrops (less than about 2 mm diameter) are approximately spherical. As they get larger (to about 5 mm diameter) they become more doughnut-shaped. Beyond about 5 mm they become unstable and fragment. On average, raindrops are 1 to 2 mm in diameter. The biggest raindrops on Earth were recorded over Brazil and the Marshall Islands in 2004 — some of them were as large as 10 mm. The large size is explained by condensation on large smoke particles or by collisions between drops in small regions with particularly high content of liquid water.

Surface area is the area of a given surface. Roughly speaking, it is the "amount" of a surface (i.e., it is proportional to the amount of paint needed to cover it), and has units of distance squared. Surface area is commonly denoted S for a surface in three dimensions, or A for a region of the plane (in which case it is simply called "the" area).

The following tables gives lateral surface areas S for some common surfaces. Here, r -denotes the radius,h- the height, e -the ellipticity of a spheroid,p - the base perimeter,s - the slant height,alpha- the tube radius of a torus, and the radius from the rotation axis of the torus to the center of the tube (Beyer 1987). Note that many of these surfaces are surfaces of revolution, for which Pappus's centroid theorem can often be used to easily compute the surface area.

surface area of sphere is
=4/3*pi*r^3
It is an effect of surface tension.
(surface tension is an effect within the surface layer of a liquid that causes that layer to behave as an elastic sheet. This effect allows insects (such as the water strider) to walk on water, and causes capillary action.

Surface tension is caused by the attraction between the molecules of the liquid by various intermolecular forces. In the bulk of the liquid each molecule is pulled equally in all directions by neighboring liquid molecules, resulting in a net force of zero. At the surface of the liquid, the molecules are pulled inwards by other molecules deeper inside the liquid, but there are no liquid molecules on the outside to balance these forces. (There may also be a small outward attraction caused by air molecules, but as air is much less dense than the liquid, this force is negligible.) All of the molecules at the surface are therefore subject to an inward force of molecular attraction which can be balanced only by the resistance of the liquid to compression. Thus the liquid squeezes itself together until it has the locally lowest surface area possible.)

Answer 5

Raindrops vary in size from about 0.02 in. (0.5 mm) to as much as 0.33 in. (8 mm) in thunderstorms.
They are spherical because all the sides of the raindrop are subjected to equal levels of pressure.