4 ms·
> We are going to focus on the two types of dry friction: static and kinetic. "dry friction"... As I remember the story, someone was trying to replicate Arrhen
by mncharity 8y ago
> We are going to focus on the two types of dry friction: static and kinetic.
"dry friction"... As I remember the story, someone was trying to replicate Arrheniius's equipment and results. The results weren't matching, until they took the equipment to an outreach event... where it got covered with greasy fingerprints. Turns out, it's Arrheniius's law of large objects sliding on pig fat.
We actually now understand friction down to nanoscale. Something that wasn't true a decade ago. But I've never seen introductory friction content written to reflect that.
- lilgreenland 8y agoI'm not that knowledgeable on friction. Do you think the friction equations are OK for high school level physics? Would you say that this is accurate? "Kinetic friction is primarily caused by chemical bonding between surfaces; however, in many cases roughness is dominant."
- mncharity 8y agoMy very fuzzy impression is HS friction is more roughness and debris than adhesion?[1] [1] "Bridging from Atomic Forces to Macroscopic Friction" http://online.kitp.ucsb.edu/online/suspensions-c18/robbins/ http://online.kitp.ucsb.edu/online/suspensions-c18/robbins/ . And the preceding "Contact of rough solids" http://online.kitp.ucsb.edu/online/suspensions18/robbins/ http://online.kitp.ucsb.edu/online/suspensions18/robbins/ . Robbins also has an old 2004 AJP article "Understanding and illustrating the atomic origins of friction" http://dx.doi.org/10.1119/1.1715107 http://dx.doi.org/10.1119/1.1715107 , but I've not skimmed it, nor explored its cited-bys for something similar but more recent.
- mncharity 8y agoERRATA: Not Arrheniius: Amontons' laws; da Vinci's experiment.[1] [1] Slides 2 and 3 of http://online.kitp.ucsb.edu/online/suspensions-c18/robbins/ http://online.kitp.ucsb.edu/online/suspensions-c18/robbins/