Could a Tyrannosaurus Rex bite through a modern day tank?
Per Glasstone and Sesonske’s Nuclear Reactor Engineering, “Alpha phase uranium is “soft and ductile, Beta phase is hard and brittle and Gamma phase is very soft”. Therefore I don’t believe the depleted uranium would help with a T-Rex on the battlefield.
via @rands
Bend LEGO Bricks, Learn Some Non-Euclidean Geometry
The slight bendability of the small 1×2 and 1×3 bricks, combined with mathematical principles has allowed Sanders to keep building up and out with his designs. Right now, the largest, a “sunflower,” [picture at link] is made of more than 1,800 bricks.
Calamities of Nature’s fill-in-the-Blank form to make you sound like Deepak Chopra. If, for some unfathomable reason, you wanted to sound like Deepak Chopra.
Chocolate printer crafts sculptures from cocoa
Using new digital technology, a printer designed by researchers in England allows you to create your own designs on a computer and reproduce them physically in three dimensional form in chocolate.
Brian Goggin, S.F. Artist, is Hauling a Colossal Block of Ice From Greenland to Manhattan
In a bid to remind the public of the effects of global warming, Goggin has decided to travel to Greenland, extract an “enormous monolith” of 100,000 year-old rare blue basal ice, and transport it back to Manhattan.
This being art, things then get weird. Well, weirder. The method of extraction is unusual. Then there’s this.
Once it arrives in New York, the ice block will be placed in a custom-designed high-tech reliquary filled with sub-zero glycol solution to keep the ice chilled, weighing in at 4000 pounds altogether. The installation will include a circle of laser beams around the reliquary that serve no practical purpose, but are intended to convey “a sense of rarity and significant value.”
I have to note that I am often encircled by lasers, but they do not seem to convey a sense of rarity and significant value. That I’ve noticed, anyway.
Ultimately, after touring museums across the nation, Goggin will install the monolith in a permanent home, where he hopes to preserve the ice for exactly 488 years. Goggin picked this number because 488 years ago, Manhattan was discovered by Captain Giovanni da Verrazzano of the French ship La Dauphine.
I hope the refrigeration unit will be run by a renewable energy source if this is to bring awareness of global warming and not be a big carbon source.
It’s been my job to wind coils in the lab, and at some point I acquired a strong rare-earth magnet, so I decided to play around with Faraday’s law: A changing magnetic fields will induce a potential difference in a loop of wire, and with many turns present in a coil each turn can contribute, so this can be be a significant effect. I set up an oscilloscope to measure the voltage in the coil and took some movies, which allowed me to grab good still shots and do this without needing more than two hands or a prehensile appendage.
Faraday’s law tells us that
\(V = -Nfrac{dphi}{dt}\)
So lots of windings (N) helps, and the driving effect is the rate at which the flux changes.
Here’s what the signal looks like when I pushed the magnet in and the pulled it out after a short delay (and repeated as necessary); you can see the pulse as the coil sees an increasing field (and therefore flux) as it gets closer to (and enters) the coil, and then the signal drops back to zero when the magnet stops moving.
But that’s not the only way for the coil to see a changing magnetic field. You can flip the magnet, and this actually induces a larger voltage in the coil
You can see that this gives a signal about 4x as large as the simple motion; flipping the magnet with my fingers happened quickly, and changing the direction by 180º gives you the maximum change in the flux that you can achieve, and you get a change in sign as well — the flux starts out at a maximum inside the coil, and the rotation causes it to decrease, increase again, and is a constant when the rotation stops. Decreasing and increasing flux give opposite signs for the induced voltage.
So what happens if you combine the two motions? Here’s the signal from dropping a spinning magnet through the coil
I think the signal here can be broken up into two parts: the drop and spin is before the center division, and the behavior from ~50 milliseconds before that division is from the magnet bouncing off of the carpeted floor and coming to rest. The drop & spin, show the envelope of the motion we see in the first plot with the oscillating behavior of the spinning. It looks like there are 5 rotations during the drop, which was from ~1 meter (though the coil itself is shorter), which would take ~450 ms. In the first part of the curve the magnet is still outside the coil, so the flux is getting bigger, which means the signal size increases. I’m not exactly sure why the signal amplitude levels off in the second half of the drop; it’s entirely possible the magnet’s rotation axis was changing direction as it fell, and any component along the axis of the cylinder won’t contribute to the signal we see here. It would be nice to have an independent way of measuring the spin effects to match them up with the electronic signal; this might be a reasonable physics-101 lab measurement to do.
How Much Ice Do You Need For Your Drinks?
The Navy has an ice command, and I assume its members always bring ice to parties simply because the partygoers assume they will, and would be angry if they didn’t. Self-fulfillment. Aka a feedback loop.
Anyway, Rhett does the calculation of how much ice it takes to cool a drink down if you own an ideal cooler, and find that a 12 oz (355ml) can of water is cooled to 0ºC with just 100g of ice. Being a responsible physicist, he does a reasonability check:
[I]f I have a 6 pack of drinks, I would need 600 grams of ice, a 12 pack would need 1.2 kg of ice. Yes, that seems small. Remember this is the ideal case.
I like to look at this another way. This tidbit stems from a NOVA show on getting things cold (Absolute Zero, which aired just before I started blogging — which explains why I can’t find a blog post on it) they explained how people used to ship ice to the tropics and made a big profit on it, and this was made possible because the amount of energy to melt a certain mass of ice was equal to the energy to subsequently heat it up to ~80ºC. We can check this by dividing the latent heat of fusion (334 J/g) by the specific heat (4.18 J/g-K) and we get that answer. Which means that freezing/melting ice involves a LOT of energy compared to changing its temperature by a few degrees. If 80ºC requires an equal mass, cooling by a quarter of that should require a quarter of the ice, plus a little for cooling the aluminum. Which gives you the 100g/can ideal case. (I guess the true “ideal case” would then be 2.4 kg of ice)
Note the recoil when the Roman candle fires (there’s one clear instance of this). Conservation of momentum.