Wikipedia:Reference desk/Archives/Science/2023 March 4

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March 4

Oil packets for instant soups

When preparing an instant soup I've noticed that the oil/fat from the plastic packet comes out with difficulties when squeezed, recently I used a toothpick to pick up the oil remnants and drop them into the soup. Is it theoretically possible to design a packet from lipophobic material or in some other manner so that the oil/fat would come out easily? 212.180.235.46 (talk) 13:21, 4 March 2023 (UTC)

Not an answer but a tip. If you first immerse the packet in hot water (or soup), the contents will come out more easily.  --Lambiam 14:40, 4 March 2023 (UTC)

Indeed. Another solution would be a disc shaped bag, no corners.Greglocock (talk) 20:47, 4 March 2023 (UTC)

The packet soups I use are dry powder, which leaves almost no residue in the packet, but being stingy I like to extract the last traces by pouring a small amount (say a tablespoon / ¹/₂oz / 15ml) of hottish water (from an electric kettle) into the packet, slosh it about, and then add it to the soup. I imagine this would also work to extract more liquid oil/fat residues. {The poster formerly known as 87.81.230.195} 51.198.55.125 (talk) 23:10, 4 March 2023 (UTC)

A problem with the plastic oil packets is that they are too tight for sloshing, especially in the corners. It may be theoretically possible to apply an oleophobic coating to the plastic, but packing just a wee bit more oil for less toothpicky customers is almost certainly less costly.  --Lambiam 09:12, 5 March 2023 (UTC)

Rolling vs wind resistence

If I stand near a highway and a relatively unaerodynamic vehicle like a pickup truck appoaches at 70 mph, I hear mainly tire noise, even though the wind resistence increases as v squared. Under these conditions, how do the energies required to overcome rolling and wind resistences compare? 24.72.82.173 (talk) 19:28, 4 March 2023 (UTC)

Must be road surface dependent, at 60 kph full throttle on asphalt a modern car generates roughly equal amounts of engine-related, tire, and aero noise. Tire noise is probably linear with speed, aero v^2, and engine noise is irrelevant on flat roads at constant speed. Hence at high speeds I'd expect aero noise to dominate. Greglocock (talk) 21:48, 4 March 2023 (UTC)

See also Roadway noise. Alansplodge (talk) 12:37, 5 March 2023 (UTC)

Also see also: Rolling resistance & Drag (physics) 136.56.52.157 (talk) 18:19, 5 March 2023 (UTC)

Tyre noise and rolling resistance both depend on the tyres and road surface, but in different ways. A soft rubber mat would give low tyre noise, but high rolling resistance. Porous asphalt-concrete (popular here on motorways) gives much less noise than cobblestones, but I don't expect a large difference in rolling resistance. Air drag is mainly determined by the main body of the vehicle, wind noise largely comes from small gaps, antennas and mirrors sticking out, grilles etc.; stuff that creates vibrations in the audible range. Turbulence around the main body also creates acoustic waves, but those are infrasonic, so you don't hear them. Conclusion: the ratio between tyre noise and wind noise says nothing about the ratio between rolling resistance and wind resistance. I'm quite sure that for most road vehicles at motorway speeds, wind resistance dominates over rolling resistance. PiusImpavidus (talk) 10:33, 6 March 2023 (UTC)