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~25mph assuming a Cd of 2.1 (a smooth brick is the closest I could find) a mass of 0.194Kg and a surface area of 0.01142313m^2 (75.6mm x 150.9mm).

Of course that assumes it’s falling facing its largest surface, and not tumbling or a falling edge first. Obviously that is trickier to calculate, but 20-40mph doesn’t seem that unreasonable.

Edit: it takes ~3 seconds to reach 99% terminal velocity.



> Of course that assumes it’s falling facing its largest surface

That was what I was thinking: surely it wouldn't be stable falling face-first? Wouldn't it be more likely to either tumble or settle on an edge?


> Wouldn't it be more likely to either tumble or settle on an edge?

There's also the possibility that it behaves more like an airfoil, and starts generating lift once it's going fast enough.


This feels like calculating a "spherical horse in a vacuum", except with drag this time.


Hah, yeah. But it's a good problem solving and reasoning exercise. One of my courses in college used this book and it's very useful for reasoning about general real-world science topics: https://uscibooks.aip.org/books/consider-a-spherical-cow-a-c...


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