Wikipedia:Reference desk/Archives/Science/2023 December 28

= December 28 =

density of mercury
Hi. I'm trying to understand the answer to this question.

Assuming that the given answer on that site is correct: I don't understand why ρ is replaced with the value 3.6 * 10^3.

My understanding is that ρ is the density of mercury, so it should be around 1.35 * 10^4. At least, that's the value I get when I google "density of mercury in kg/m3".

Every other value I understand. Alpha is the surface tension of mercury in N/m. g is the acceleration due to gravity which is 9.8 m/s2. d is the diameter of the hole given in the question which is 70 micrometer. Liberté2 (talk) 00:10, 28 December 2023 (UTC)


 * I'd like to clarify that this is not a homework question.
 * I remember seeing liquids unable to escape out of tiny holes, likely due to surface tension. So I was wondering whether there's a direct relationship between minimum hole size and surface tension. Googling that lead me to this physics stackexchange  which has the correct equation. I tried to search for some actual applications of this equation which lead me to that toppr.com page. Liberté2 (talk) 00:38, 28 December 2023 (UTC)


 * I haven't the foggiest, I'd agree with you. The only thing I can think of is they stuck in the density of the wrong material, but anyone in physics would know the approximate density of mercury. NadVolum (talk) 01:03, 28 December 2023 (UTC)


 * The next step combines powers of ten and a few other factors (490 / 9.8), and the 3.6 changes to 13.6. So the 3.6 seems to be just a typo. --Amble (talk) 02:06, 28 December 2023 (UTC)
 * Thank you!!! It's indeed a typo. Liberté2 (talk) 05:24, 28 December 2023 (UTC)
 * I should have noticed that, silly me, thanks. The 3.6 had nagged me a bit but I hadn't thought about it properly. NadVolum (talk) 14:25, 28 December 2023 (UTC)