Beijing 2008 – It’s a wrap at The Big Picture (39 photos)
If you look at the high jump of Blanka Vlasic, you can see how it’s possible to do a high jump with your center-of-mass (focus on the physics) never rising above the bar, though I think in this jump it is higher, since she’s clearing the bar by a bit. But I would guess that her COM is below her torso.
And that last one is going in my desktop picture rotation.
Oh, way cool. A rotating grid looks like a bunch of smaller grids when you rotate it.
I notice that the answers are posted for the “Presidential Physics quiz” in the NY Times (original quiz wording) and, well, blech. Sorta. I’ve read decent things about the Physics for Future Presidents book, but I don’t want this to be the example for “how to quiz presidents and justify the answers.”
QUESTION 1. How does the amount of energy per gram of TNT compare with the energy per gram of a chocolate chip cookie?
My answer is (d), the cookie contains nearly 10 times as much energy.
But the answer is really around 5 or 6, depending on what numbers you’ve used, and one of the other choices is “about the same.” If you’re going to do multiple-choice, try not to bracket the right answer this way.
I do like the defense of discounting the E=mc2 answer, because it shows recognition that we’re dealing with chemical rather than nuclear reactions. But in the defense of the answer, there’s
TNT explodes all by itself, no air needed.
Well, no, not really. If you balance the reaction, you’ll find that significant oxygen is needed. Sugars have oxygen in them, too. You still need external oxygen for that reaction as well.
But all of this ignores that science isn’t just a bunch of facts. What I’d rather see from a president (or student) is some reasoning, like “these are both basically combustion reactions, so to first order, I’d expect them to release similar amounts of energy” and worry about the details later on, like what difference there is because you have some nitrogen in TNT, and how that might affect the bottom line, and maybe the reasoning that you give up some energy for the convenience of a reaction that forms more moles of gases (and those gases want to occupy 22.4L each at STP, so boom!) instead of keeping the molar amount of gas the same (swapping CO2 for O2).
QUESTION 2. Based on the answer to the previous question, suggest an energy-efficient way to destroy a car.
Teaching evolution — and, by the sound of it, doing a good job — in Florida. He realizes that if the science sounds dogmatic he’s lost before he even starts.
A Teacher on the Front Line as Faith and Science Clash
When Florida’s last set of science standards came out in 1996, soon after Mr. Campbell took the teaching job at Ridgeview, he studied them in disbelief. Though they included the concept that biological “changes over time” occur, the word evolution was not mentioned.
He called his district science supervisor. “Is this really what they want us to teach for the next 10 years?” he demanded.
In 2000, when the independent Thomas B. Fordham Foundation evaluated the evolution education standards of all 50 states, Florida was among 12 to receive a grade of F. (Kansas, which drew international attention in 1999 for deleting all mention of evolution and later embracing supernatural theories, received an F-minus.)
Who needs a lever, man? I’m Marty McFly.
Let’s say, for the sake of argument, that you needed to move a heavy piece of equipment you’re helping to build. And you have the constraints of not wanting to tip it, and the course you need to navigate has some spots with less than 10 cm of overhead space. (This ignores one doorway that’s actually 10 cm too low — yes, we’ve done the equivalent of having built a boat in our basement. The solution there will either be slapping Daffy Duck with a frying pan in the shape of the equipment and having him run through the door, or a sawzall.) You need a smooth ride, because it’s an expensive, somewhat delicate trinket representing a several dollars and a few person-years of labor.
I tried designing a cart, but couldn’t meet all of the constraints — anything low enough would tend to bottom out on the incline (oh, that’s right, the path isn’t level the whole way. Is that a problem? I need this soon.) One day I was stressing and kvetching about it in front of the right person, who suggested air bearings/air casters. The heretofore unconnected link between the physics and the application clicked, and I knew that was the answer. Float the sucker on air. A small industrial blower and lots of small holes.
Here’s a demo of the system with a dummy load. There are also some lead blocks there, too. (cue rimshot). 160 kg for the optical table, lead and support structure, and another 110 kg or so for me.
(if you want a soundtrack, turn on a vacuum cleaner. Any “Ishmael” wisecracks about my pasty-white legs will be subject to retaliatory editing)
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most beautiful land speed record vehicles
picks purely based on looks rather than actual speed
I know water polo is a taxing sport, and it’s great that the US took a silver. But watching the players walk along side the pool, I couldn’t help but thinking their headgear looked like baby bonnets, and that they looked like giant infants.
Ten ancient observatories spied from space
Image taken by GeoEye’s Ikonos satellite at 400+ miles above earth.