Category Archives: physics in action

physics in action, zeppelin

The Best Blog Title Evar…

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It’s Hard Up Here for a Blimp

The maiden flight of the Airship Ventures first blimp. Guess its name and win free flight!
The maiden flight of the Airship Ventures first blimp. Guess its name and win a free flight!

Okay, so Wired beat me to it, but you gotta admit, it’s a great title. And, the story behind it is one that I’ve known about since last year when one of the two principals told me about it at a meeting.  The “blimp” in question is actually a zeppelin (essentially a blimp with rigid airframe) — and the first to touch down on American soil in more than 70 years. It doesn’t have a name yet, but it belongs to a company called Airship Ventures, founded by a couple named Brian and Alexandra Hall.

Alex is an old friend and colleague who we got to know from her work with a couple of different science center fulldome theaters in England and the U.S.  I ran into her at an Association of Science-Technology Centers meeting in Los Angeles a year ago and she regaled me over lunch with the tales of hers and Brian’s latest adventure.

I have to admit, I’ve wondered how this venture would go, considering that zeppelins haven’t been used much for human transport in an age of jet aircraft.  Still, we’re all used to seeing the Goodyear Blimps (which are different in design but follow the same principles as zeppelins) in the skies over games. So the idea of gliding along in an airship that lets designers take advantage of the way gases can be compressed (remember the gas laws!) into bags (cells) that can be attached to rigid skeletons and used to loft people into silent flight isn’t a new one. I hope it goes well for Airship Ventures — and maybe sometime I’ll be able to save up and take a ride with Alex and Brian!

physics in action, trebuchet

The Atomic Bomb of the Middle Ages

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or, The Physics of Punkin’ Chunkin’

What could be more geeky than going out on a beautiful fall afternoon and watching some guys do physics? Not much, I’ll admit. But, that’s what we did this weekend and by golly, we enjoyed watching guys hurl, just as folks have been doing ever since the Middle Ages, when flinging rocks at your enemy’s castle was the state of the art in warfare. Only this time it’s more peaceable — the guys we watched were hurling pumpkins more than 2,000 feet at a pop.

The trebuchet at Yankee Siege hurled a pumpkin more than 2,000 feet on October 12, 2008.
The trebuchet at Yankee Siege hurled a pumpkin more than 2,000 feet on October 12, 2008.

The occasion was the Punkin Chunkin practice shooting at Yankee Siege in Greenville, New Hampshire. They don’t hurl with their hands — they use a trebuchet.  Those of you who are Northern Exposure fans may recall that in one episode they hurled a piano into a creek using a trebuchet.  Those of you who are physics fans have probably already created your own trebuchet and flung stuff with it.  You can learn  more about trebuchets at Trebuchet.com, where they have all kinds of discussions about hurling stuff, feature some books and, of course, simulators and desktop trebuchets for sale.

So, aside from howling and stamping and laughing and clapping as these guys wound up their siege engine and hurl a pumpkin almost half a mile, what’s the deal with these things? Why the fascination?

A trebuchet is basically the oldest projectile weapon machine in the world. It was used in the Middle Ages to strike fear into the hearts of opponents, and it was fairly easy to build with the materials at hand.  All you needed was a sling to hold the load (your basic rock as a weapon) and a structure that used a lever arm to hurl the rock.

The lever and swing principle behind the trebuchet. Courtesy of Thinkquest.org.
The lever and swing principle behind the trebuchet. Courtesy of Thinkquest.org.

A lever arm works by sticking something on one end of a stick or board and then dropping something heavy on or from the other end (a counter-weight) .  The projectile load goes flying off, hopefully toward your opponent. It’s like a see-saw, only a lot bigger and more dangerous and ‘way more complex, as you can see by the picture of Yankee Siege’s trebuchet.

It’s physics, man.  And, when you watch them wind it up, get it loaded, and then let some little kids tug on the rope that launches the trebuchet, it’s a thing of beauty to watch that regulation pumpkin soar into the air in a perfect arc.  People stand up and cheer and hoot and holler.

Maybe you don’ t have a trebuchet in your neck of the woods, but that’s no reason not to play with one and do a little physics at the same time.  Take the Treb Challenge by building your own virtual trebuchet and flinging some weight around.  And remember, as they say at The Hurl, it’s not what you hurl, but the hurl itself that matters!

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