Physics of a bicycle visually explained

Riding a bicycle is a seemingly simple activity that we never forget how to do. However, the physics behind pedaling and movement is a balance between force and resistance. Bartosz Ciechanowski breaks it down in a visual essay filled with interactive demos.

The structure of Ciechanowski’s essays are straightforward with the interactives doing a lot of the heavy-lifting for every concept. The physics are split into many small parts for ease of understanding. It makes me wonder about a data visualization equivalent to explain a complex dataset.

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Fracture and flow of Oreo cookies

Crystal Owens, Max Fan, John Hart, and Gareth McKinley from Massachusetts Institute of Technology published their research on how the cream in an Oreo behaves when you split the sandwich, in Physics of Fluids:

Using a laboratory rheometer, we measure failure mechanics of the eponymous Oreo’s “creme” and probe the influence of rotation rate, amount of creme, and flavor on the stress–strain curve and postmortem creme distribution. The results typically show adhesive failure, in which nearly all (95%) creme remains on one wafer after failure, and we ascribe this to the production process, as we confirm that the creme-heavy side is uniformly oriented within most of the boxes of Oreos. However, cookies in boxes stored under potentially adverse conditions (higher temperature and humidity) show cohesive failure resulting in the creme dividing between wafer halves after failure. Failure mechanics further classify the creme texture as “mushy.” Finally, we introduce and validate the design of an open-source, three-dimensionally printed Oreometer powered by rubber bands and coins for encouraging higher precision home studies to contribute new discoveries to this incipient field of study.

This is very important. [via kottke]

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What is a particle?

Natalie Wolchover for Quanta Magazine asked several physicists what a particle is. She came away with several points of view. For example, the particle as a “irreducible representation of a group”:

It’s the standard deep answer of people in the know: Particles are “representations” of “symmetry groups,” which are sets of transformations that can be done to objects.

Take, for example, an equilateral triangle. Rotating it by 120 or 240 degrees, or reflecting it across the line from each corner to the midpoint of the opposite side, or doing nothing, all leave the triangle looking the same as before. These six symmetries form a group. The group can be expressed as a set of mathematical matrices — arrays of numbers that, when multiplied by coordinates of an equilateral triangle, return the same coordinates. Such a set of matrices is a “representation” of the symmetry group.

Oh boy. A lot of this was over my head, as I nearly failed physics in college, but the various explanations with basic diagrams taught me a few new things.

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How gears work

Bartosz Ciechanowski took a deep dive into how gears work and the physics behind the movement with a series of graphics and interactives:

I’ve always been fascinated by mechanical gears. There is something captivating about the way their teeth come together to create a fluid, unified motion.

In this blog post I’d like to look at these simple machines up close. I’ll explain how gears affect the properties of rotational motion and how the shape of their teeth is way more sophisticated than it may initially seem.

[Thanks, @mtoconnor3]

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Gravity visualized in physics demo

Dan Burns explains some properties of time and space using marbles and two large pieces of spandex sewn together in a classroom demonstration.

https://www.youtube.com/watch?v=MTY1Kje0yLg

Physics and me never got along in high school and college, but I did always enjoy the low-budget demonstrations. It's one thing to see calculations on paper. It's another when the professor sets up a stuffed monkey on one side of the room and then shoots a sock out of a pressurized cannon angled at the trajectory you just calculated to make sure the sock hits the monkey on its way down from ceiling height.

Of course you can look it up on YouTube:

https://www.youtube.com/watch?v=cxvsHNRXLjw

In retrospect, shooting a monkey falling out of a tree seems kind of wrong.

And while we're at it, I always liked this demo too. A bicycle wheel gyroscope hangs from a rope, and when it spins its axis stays horizontal like magic.

https://www.youtube.com/watch?v=8H98BgRzpOM

MIT has a 43-demo playlist if you need something to watch during your lunch hour.

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Skateboard physics

Physics of an Ollie

Aatish Bhatia, a recent physics PhD, describes the forces involved to do a skateboard Ollie. It's all about managing your center of gravity and applying variable amounts of torque to steer the board in the air. Yeah. It probably won't help you skate any better, but it'll help you appreciate the tricks a little more. [via kottke]

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