Is spider web really stronger than steel?

I was not expecting an excellent explanation of stress-strain curves (2:30), toughness (6:00), environmental costs of polymer production (7:00), amorphous vs (nano)crystalline regions (6:45), hydrophobicity (and hydrophilicity) (12:45), and CRISPR/Cas9 technology (20:30), but that's what you get in today's Veritasium video.

As an aside, I want to rant and rave about the investment in Veritasium by Electrify, but the quality of the videos, the topics being covered, and the volume of output have stayed at least as high and might in fact have improved.

How NASA Reinvented The Wheel

If you're a long-time blog follower, you might be wondering if this isn't a repeat posting, but it's not.

I did previously post a video titled How NASA Reinvented The Wheel - Shape Memory Alloys, but that one was by Brian at Real Engineering.

The topic are largely the same, though this one goes more deeply into how NiTiNOL works on the stress-strain curve and how the deformation of NiTiNOL is an autenite to twinned martensitic crystal transformation - complete with some nice animations.

It does also mention that the crystal transformation are exo- and endothermic (17:05), something that I don't think I've seen mentioned in other videos. I admit that if hot water is necessary for the martensite to austenite transition, it must be endothermic, but I haven't seen anything demonstrating that transition being both noticeable with bare hands - and a large enough NiTiNOL sample - or via thermal imaging camera. Neat detail there, doctor Derek.

Understanding Material Strength, Ductility, and Toughness

Strength vs toughness is such a subtle concept for my students to understand.

That isn't really a tough (sorry) thing to reason out. The two words are used somewhat interchangeably in the non-material science world. 

This video does a great job animating and showing the differences between those words and using the stress strain curve to do so. 

Explaining the Stress-Strain Curve with a Paperclip

Last week I said I was going to check out what else the Mat Sci Guy had posted, and I found the above video explaining the stress-strain curve 'with a paperclip'.

Again, be warned, his narration is less than exciting, and the level of science can be a little high for at least my students.

But the explanation of how a paperclip can demonstrate the stress-strain curve is really good. He breaks down the elastic and plastic deformation regions of the curve and explains how those changes are different on an atomic level using two-dimensional diagrams while showing that on a macroscopic level with an extra-, extra-large paperclip.

I appreciate him providing the explanation on the macroscopic, symbolic, and particulate levels, something we've seen within the AP chemistry as a recent push.

Oh, and there are fewer corny jokes in this week's video than in last week's. Other than the 'what is a paperclip used for' schtick at the beginning, it's a pretty straight forward video.

The Physics of Slingshots 2 | Smarter Every Day 57

I keep wanting to tell Destin that he's gonna shoot his eye out.

But it looks like he still has his predator vision at the end of this video, so that's his business as to whether he wears goggles or not.

At 2:13, Destin shows a graph of the potential and kinetic energy of the ball/band system as the band stretches and releases.

At 4:39, he then uses actual data/video to show that a tapered slingshot band accelerates the bullet faster than does an un-tapered band.

Then, at 5:00, our favorite - the stress-strain curve - shows up.

Sadly, some of the links in the video description to learn more about hysteresis, for example, are dead.

Destin got two videos out of his visit with Jorg (check the slingshot channel for even more). The other video doesn't have as much material science content, but it's still fun, and it shows some momentum and energy calculation with a gigantic slingshot.

COLD HARD SCIENCE: SLAPSHOT Physics in Slow Motion - SmarterEveryDay

Yes, a hockey player with a missing tooth is frighteningly stereotypical.

The sight of the hockey stick at full flex - in motion at about 2:35 - is outstanding...as is the idea that the player likes his stick 'whippier'.

I'm not a hockey player, but I was a tennis player, and I understand the same idea in a different application. Players can choose how much tension they want in their strings when the tennis racket is strung. Stringing at a lower tension allows the ball to deflect the strings more, creating more of a trampoline effect and generating more power. The cost to that is a decrease in control - worse aim - because of that increased power.

Here's a second video going through the same physics - for the first seven minutes anyway. After the first seven, we get a look at the physics of a wrist shot and a hockey player's workout.

Personally, I prefer Destin's enthusiasm.

Concrete Stress Strain Curve (early age 4 days)

We're working on understanding the stress-strain curves today at master teacher training at the ASM dome (love this place), so I'm searching for examples of a tensile test being performed at the same time that a stress-strain curve is being generated.

First find...a concrete pillar being tested.