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The Physics of a Rolling Rubber Band

Posted by CmdrTaco on from the thank-god-that-is-solved dept.

sciencehabit writes "Modern physics can get complicated. Sure, researchers know exactly what forces act on a ball rolling down an incline — an experiment that helped Galileo develop universal laws for movement and acceleration. But what happens when a deformable shape like a rubber band rolls around? A new study reveals that the faster it goes, the more squashed it gets (video included)."

4 of 226 comments (clear)

  1. Physics... by Pojut · · Score: 3, Insightful

    ...is mind-boggingly awesome. I can't understand the math at all, but I understand the way things generally act. So cool (and so insanely complicated! Think about something like a key being inserted into a lock...and that's just simple, everyday stuff!)

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    Living With a Nerd
    1. Re:Physics... by EdZ · · Score: 3, Insightful

      Because air behaves differently at different speeds. Once you got fast enough, shockwaves become the limiting factor rather than fluid fraction. Then you have cavitation, and things like compression heating. What is most efficient at one speed is not most efficient at all speeds.

    2. Re:Physics... by VolciMaster · · Score: 2, Insightful

      Yeah, that quote bothered me too - I'm thinking, why not just design it with the least friction with the air to start with - why have it be less efficient at slow speeds in other words?

      Unless Clanet was referring to the design process itself - use an elastic model in a wind tunnel (or simulate the whole thing) and observe it's deformation to determine the shape with the least friction with the air (or call it coefficient of drag, like everyone else does :-)

      At first I was thinking it might have been typical media-distorted science, but when they threw in that quote from Clanet, it seemed more that the science is hard to take seriously too.

      Just a quick thought, but at low speeds aerodynamic efficiency is of very low impact (eg a barge at 2 kts and a kayak at 2 kts). The faster they go, the more that efficiency matters - having a material that could deform to improve flow as speeds increased could be a good thing - especially if it were used around the freight compartments of a tractor-trailer or rail car: squishing-down to more evenly flow around the carried contents could have some promise.

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      antipaucity
  2. Re:Wow, interesting! by Chris+Burke · · Score: 2, Insightful

    Yeah, stupid meteorologists, talking about "cold fronts". No such thing! They should say "Fronts containing less heat." But then again all fronts contain heat, so what's a warm front? It's just warm compared to cold fronts.

    Maybe it's because of my electrical engineering schooling and years spent acting as if it was the positive charge carriers that were moving, but I don't see any problem with saying "let the cold in". Cold is a negative heat delta. Big whoop. When you open the door in the winter, cold air blasts you in the face, cold air got in the house, and the house becomes colder. You let the cold in.

    "Cold" may not exist but the concept is valid, and you can only tell the difference because of absolute zero. It's very similar to negative energy, a common concept in physics. The question of whether or not it "exists" vs is a valid way to conceptualize energies that only average to zero, is just how you view it.

    There are legitimate contexts where it is 100% pedantically accurate to talk about things that don't exist.

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    The enemies of Democracy are