Why Raindrops Don’t Kill Us…

I’d never really pondered the idea that raindrops might be a cause of death until the other day.

If we’re concerned about killer pennies from the top of the Empire State Building, how much more scary are little water bombs from thousands of feet in the sky?
No need to fear…physics is here!!!
Since raindrops are relatively small in volume, the reach a small terminal velocity quickly. An explanation follows:
When raindrops fall, they are met with air resistance. Air resistance is proportional to surface area, so small and big raindrops experience the same phenomenon. The air continues to resist the raindrop until air resistance reaches the same value as the gravitational force. This moment is when the raindrop reaches its “terminal velocity”. It can’t go any faster because it’s no longer accelerating. 
And since rain drops have little mass, they won’t have a very large velocity!!
Good thing there’s air resistance between the clouds and the ground!
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3 responses to this post.

  1. Very true…never though of it that way….hail can be tough at times….what actually happens when it hails? They can get really big.

    Reply

  2. Posted by rebbieg on April 30, 2009 at 6:34 pm

    Fabulous question! I’ll work on that one and write a new post!

    Reply

  3. […] physics education, physics teaching, science teaching trackback In the original post about Why Raindrops Don’t Kill Us, I showed why raindrops falling from the sky do not kill us. Some clever reader wondered what would […]

    Reply

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