Why the raindrops are sharp at the top and narrow at the bottom

When a raindrop is stationary in the air, it is subjected to two forces: gravity and buoyancy, which are equal in magnitude and opposite in direction. When gravity is greater than buoyancy, it moves downward; In the course of motion, a third force is subjected:

Frictional force. The friction causes the raindrop to change its status quo and become an inverted exclamation point shape with a lower circle and a sharp point, where friction is minimal.

As the air currents moved, these small droplets kept moving, colliding with each other, and several small droplets became one large droplet. When the water droplets are so big that the air can't hold them, they become raindrops. But the raindrops, no matter how big or small, are not teardrop-shaped, and many of the drawings are not right.

The base of the heavy raindrops is somewhat flattened, but most of them are rounded. This is because the water droplets have a condensed nature, so the raindrops are round).

Why are there big and small raindrops?

The size of the raindrops varies depending on the nature of the rain clouds.

The factors that determine the size of raindrops are mainly determined by the amount of water vapor in the air and whether the vertical motion in the clouds is strong. The more water vapor content and the stronger the vertical motion, then the greater the raindrops.

In summer, the wind blows from the ocean, the air is rich in water vapor, and the temperature of the ground is very high, the convective movement of the air is very strong, a large amount of water vapor is brought to the high altitude, because the temperature drops, it condenses into water droplets, and clouds appear in the sky; If the convective movement is very strong, the cloud will become very thick and large, like a large mountain, and if it produces fibrous filaments with silk luster on the top, it means that the cloud has reached its peak stage, and this kind of cloud is called cumulonimbus in meteorology.

In a cumulonimbus cloud, the water droplets are large and constantly colliding and merging with each other, making the water droplets larger and larger until the strong updrafts in the cloud can no longer be stopped, and they fall down to the ground and become rain. Therefore, the raindrops during a heavy thunderstorm can be regarded as the largest. According to field measurements, the diameter of raindrops during heavy rains is generally 3-4 mm, and the maximum can reach 6-7 mm.

Secondly, when a typhoon hits the southeast coastal area of China in summer, the typhoon also has the characteristics of more water vapor, strong convection and thick clouds, so the raindrops of the typhoon rain are also very large.

The smallest drop of rain is drizzle, and its diameter is less than a millimeter. Because the clouds are thin and the air is stable, and the water vapor is not very abundant, the raindrops are very small, and they float erratically when they fall, and they do not ripple when they fall to the ground.

However, even within the same rain cloud, the size of the raindrops that fall is different. This is because the raindrops are formed by the enlargement of cloud droplets, and the original cloud droplets are not equal due to the different sizes of the condensation nuclei and the different sequences of condensation, and the water of the large and small droplets is easily transferred from the small droplets to the large droplets due to the different water vapor pressure, so that the large droplets continue to increase, and the small droplets will also become smaller. Moreover, the water vapor content, temperature, turbulence, the number of cloud droplets, the strength of the updraft, etc., are not the same in each part of the cloud, so the condensation increase rate and the collision and merger increase rate of the cloud droplets are not the same, and the thickness of the cloud is different in each part, and the time and distance of different cloud droplets moving in the cloud are also different, the time is long, the distance is long, the water vapor transfer between the large and small cloud droplets is more, and the number of collisions and mergers is also more, so that the difference in the size of the water droplets is more obvious.

After the raindrops fall out of the clouds, the conditions for evaporation are also different.

For all these reasons, the size of the raindrops falling from the same rain cloud is different.

Simply put, it's because of the Earth's gravity.

Raindrops When falling from a high altitude, the gravitational potential energy is converted into kinetic energy, and the speed of descent is getting faster and faster, and the upper part of it will fall rapidly due to inertia, and the upper part will fall downward, so the raindrops will be sharp and sharp.

You have observed very carefully, because of gravity, it will be larger than the top, so what would be the effect of building a steel ball factory in space?

Friction causes the raindrops to change shape and become streamlined, as well as liquid surface tension.