In an article in today’s Physical Review Focus, Chelsea Wald describes recently published research that shows how, under special circumstances, balls can bounce from a surface with a higher vertical speed than they had coming in – a “coefficient of normal restitution” greater than one. The original paper on this, by Michel Louge and Michael Adams, describes experiments in which a hard aluminum oxide sphere was thrown at a thick plastic plate, and some images of the impacts are available on the Focus site. The new paper is a theoretical study, with some simulations, which indicates that this effect works when the impacting ball is harder than the surface, and deforms it in certain ways. This apparently has interesting implications for the study of granular materials, not to mention other applications where balls rebound from surfaces.
2 thoughts on “Secrets of the Upward Bounce”
Comments are closed.
Believe it or not, the human mind has made accommodation for this type of effect in iconic linguistic encoding. Objects or surfaces (of different shapes) hit by others are usually thought of by researchers to be capable of either absorbing or reflecting some or all of the energy of impact (often coming from viscous, viscoelastic, or elastic properties of the impacted material, in concert with those of the impactor).
But these are not the only logical possibilities. Impacted objects and surfaces can also donate energy to an impactor, but obviously to do so means either that the impacted material either stores already or can transfer such energy from other sources. In many languages one sees iconic terms (ideophones- like onomatopoeia just much more involved and covering many more physicomechanical phenomena than just sound) where this is encoded in an initial palatal sound (similar to English j, ch, ny, etc.). In such words the reflected impactor (which may be free, or an attached part of something else) gains extra momentum from the interaction, even sometimes enough to send it zooming away out of sight.
For such arrangements of mass, energy, space, and time to be universally similarly encoded linguistically as above implies that our genetically inherited brains have internalized such physicomechanical relations, either entirely genetically or in concert with interaction with the enviroment. Animals seem to have similar understandings, though it is unknown if they encode them in communication.
From this perspective it is interesting that physicists find natural instantiation of such interactions so amazing- I have had to play with such ideas for a long time in my linguistic work, and figured that this kind of thing would have been par for the course. Who coulda guessed?
Codemaniac
er… What?