A playground ball finds stability in a saddle when the saddle is rotating at the proper speed.
Mechanical analog of a “Paul Trap” particle confinement—a ball is trapped in a time-varying quadrupole gravitational potential. A large saddle shape (attached to a plywood disk) is mounted on a multi-purpose turntable. The saddle shape is essentially a quadrupole gravitational potential. Rotation of this potential subjects the ball to an alternating repulsive and attractive potential, much like the time-varying electric quadrupole potential of a Paul Trap used in trapping single ions or electrons.
The plastic ball used here is about 25 cm in diameter and was purchased at a toy store. The saddle consists of many layers of fiberglass and was hand-made with help from Justin Georgi. The turntable is driven at about 110 rpm with a DC motor. We have observed this ball at this speed remaining stable for over 2 hours.
Showing 5 posts tagged spinning
On older buildings, it’s not too uncommon to see the crowning touch of an ornamental weather vane — a rotation device which indicates the wind’s direction. But what happens when a bunch of weather vanes are put together on the same surface? That’s the question that American artist Charles Sowers answers with Windswept, a kinetic installation of 612 aluminium weather vanes placed on the facade of San Francisco’s Randall Museum — and revealing surprising results, as you can see in this video from Dezeen.
As you can see, the spinning blades don’t uniformly point in the same direction as one might expect, but rather show smaller diverse patterns and paths of the breeze. Says Sowers: ”Windswept seeks to transform a mundane and uninspired architectural façade (the blank wall of the theatre) into a large scale aesthetic/scientific instrument, to reveal information about the interaction between the site and the wind.”
From the archives, more origami.
During the process of making an orb web, the spider will use its own body for measurements.
Many webs span gaps between objects which the spider could not cross by crawling. This is done by letting out a first fine adhesive thread to drift on the faintest breeze across a gap. When it sticks to a suitable surface at the far end, the spider will carefully walk along it and strengthen it with a second thread. This process is repeated until the thread is strong enough to support the rest of the web.
After strengthening the first thread, the spider will continue to make a Y-shaped netting. The first three radials of the web are now constructed. More radials are added, making sure that the distance between each radial is small enough to cross. This means that the number of radials in a web directly depends on the size of the spider plus the size of the web.
After the radials are complete, the spider will fortify the center of the web with about five circular threads. Then a spiral of non-sticky, widely spaced threads is made for the spider to easily move around its own web during construction, working from the inside out. Then, beginning from the outside in, the spider will methodically replace this spiral with another, more closely spaced one of adhesive threads. It will utilize the initial radiating lines as well as the non-sticky spirals as guide lines. The spaces between each spiral will be directly proportional to the distance from the tip of its back legs to its spinners. This is one way the spider will use its own body as a measuring/spacing device. While the sticky spirals are formed, the non-adhesive spirals are removed as there is no need for them anymore.
(And yes, we just finished reading Charlotte’s Web.)
Making tea (a viral video) in the streets of Bangkok, Thailand. The kid should see this!