Going, Going ...

GETTING OUR BEARINGS:  This week, we dutifully, thoughtfully and carefully listened to the lectures of University of Virginia professor Lou Bloomfield for our "How Things Work" physics class through Coursera. The topic has been wheels, and it has been interesting and challenging.

We've learned about sliding friction, static friction and more about thermal energy. We learned that wheels are simple machines, and about differences between  how free wheels and powered get going (a front wheel and rear wheel of a bike was used to describe that). Kinetic energy was covered. We learned that frictional forces acting along surfaces are parallel to the surface, while support forces are perpendicular. We learned why sliding a box across a floor is usually hardest at the start (the surface of the bottom of the box and top of floor actually settle into each other a bit - they're interdigitated, perhaps my favorite new word). And we learned that tribology is the science and engineering of interacting surfaces in relative motion. (I think being a tribologist would be fascinating.)  Prof. Bloomfield also let us know that we can find coefficient of friction tables, which show the frictional relationship/relatively between different types of materials/surfaces.

We now know that Newton didn't write all the law of physics. For instance, there's Amonton's First Law of Friction, which states that frictional forces between two surfaces are proportional to the support forces between them (and we knew that an example involving this law would be on the test).

One of the things we learned was that though there's static friction between the rubber and the road, so to speak, and that's good, because that static friction allows you to start and stop moreso than sliding friction. There is, however, some sliding friction where the axle spins in the wheel's hub. Bearings (ball or roller, for instance), can be used to eliminate this sliding friction. But that's for more sophisticated wheel set ups than this rolling hamster or Happy Meal toy.

We also did a few computations involving W(ork) = F(orce)xD(istance), and Kinetic Energy= 1/2Mass x Speed².

I was soooooo happy when I hit the submit button on the quiz and saw that I scored 100 percent (especially considering I felt confident about three out of 10 of the answers). We all did a happy dance.

Speaking of bearings, in a happy coincidence, yesterday NASA was kind enough to email me a story about the major tune up their crawler-transporter (CT-2) has been undergoing for the last year-plus. The work was prompted by the greater loads NASA anticipates having with its new rocket (the SLS) designed to take astronauts beyond low-Earth orbit.

We read the story on their site, but all it had was still photos, like the one above, showing the whole crawler, and the one below, one showing where upgraded roller bearing assemblies were installed (in the blue circle below, both photos credit: NASA)

The photos are fine, but wanted to see the mammoth crawler in action! Fortunately, I found this neat-o time lapse video of it rolling from the Vehicle Assembly Building to the launch pad.


We also watched this short, informative video about the crawler and the people whose job it is (or was) to make sure the spacecraft get to the pad in one piece, so to speak.


IN OTHER NEWS: Christian got his car stolen today, along with his wallet and our identities. Happy Thursday.