Sunday, May 06, 2007

Updated: Web Video for the Classroom

The Northern California and Nevada section of the American Association of Physics Teachers (NCNAAPT) met Friday and Saturday at Stanford, I presented a talk on the Web Video for the Classroom page I maintain. Pretty groovy to see these clips on a huge screen in a Stanford lecture hall, and those in the audience seemed to enjoy the show. I added a few clips to the collection, so I thought I should jot a quick post.

No doubt there are other physics video treasures out there. Let me know so I can add them to my page.

Oh, some attendees of the meeting asked about the skeptics group and conference I referred to when showing the firewalking clip. The group is the James Randi Educational Foundation and the annual meeting in Las Vegas is The Amaz!ng Meeting.

1 comment:

Zeke Kossover said...

I love the videos, but the Brainiac: Science Abuse video about the bottom of the alkali metals is staged. Many on the Internet have spent some time debunking it. Theodore Gray

The problem is that, while cesium is very reactive, reactive doesn't mean explosive. The alkali metals are explosive because they liberate hydrogen gas, and the hydrogen gas is explosive if it can accumulate. Since cesium has a higher atomic weight than potassium, two grams -- the amount in the video -- actually releases less hydrogen than potassium does So cesium ought to make a smaller bang than potassium despite the fact that it makes a bigger one in the video.

Knowing this you might wonder why lithium, the lightest alkali metal (assuming you don't count hydrogen), doesn't make the biggest bang. The answer is that being less reactive it doesn't make hydrogen as fast or produce much heat to ignite the hydrogen. Potassium is pretty much at the sweet spot. It produces hydrogen quickly and it has a low enough atomic weight to make lots of it. Check out the link for more of the gory details.

(I showed this link for more than a year before I found out. Sigh.)