Why do raindrops falling at terminal velocity not hurt us due to surface tension?
In: Physics
Force = mass times acceleration. The velocity of a raindrop isn’t all that much comparatively speaking, and their mass is pretty negligible. Combine that with the fact that the acceleration is also reduced as the drop deforms and splatters rather than stays rigid like a rock, and it doesn’t transfer much force at all.
“Terminal velocity” does not mean “shooting at you like a bullet”. It means “the fastest an object will get in free-fall before wind resistance is slowing it down enough that it can’t get any faster”.
The terminal velocity of a raindrop isn’t much at all.
Then since its mass is almost nothing, and its velocity is nothing special, the force of impact is also almost nothing.
I don’t think anyone has mentioned this yet but the terminal velocity of raindrops is only 22mph. That’s slower than you can throw a ball and raindrops are tiny.
Their terminal velocity isn’t all that high, and they don’t weigh all that much.
It’s very different from a person falling into a pool at terminal velocity.
>In still air, the terminal speed of a raindrop is an increasing function of the size of the drop, reaching a maximum of about 10 meters per second (20 knots) for the largest drops.
[Source](https://gpm.nasa.gov/resources/faq/how-fast-do-raindrops-fall#:~:text=In%20still%20air%2C%20the%20terminal,seconds%2C%20or%20about%20seven%20minutes.)
10 m/s is roughly 22 mph, so the fastest raindrops aren’t really moving that fast.
Surface tension is negligible here. The raindrops are not very fast and they can easily break up when hitting something.
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