Physics on Etsy!

Density Column Key Fob

Avialable here: Totoro Drift Bottle Keychain

Get similar liquid key fobs here:
From Etsy: BUY NOW: Liquid Key Fobs
From Amazon: BUY NOW: Liquid Key Fobs

Density Column Key Fob: lots of physics in the design of this ridiculously cute key fob— two immiscible fluids are sorted under gravity by density with the densest on the bottom and the lightest on top (often kerosene and mineral oil). The plastic animal (best guess: rabbit?) has a density between that of the two liquids so it stays at the boundary layer, and the critter is weighted to be bottom heavy so it keeps a vertical orientation with help from Archimedes law of buoyancy. The most recent versions of this toy have interesting opaque colored liquids, such as the gray fluid featured here. 




Rolling Uphill Illusion

Availabel here:
From Etsy: BUY NOW: Uphill Ramp Illusion

or get the 3D print file here:
From Thingverse: Download Now: Uphill Illusion

Learn more: The amazing illusions of Kokichi Sugihara
See the many other Sugihara Illusions: in my collection

Rolling Uphill Illusion: the ball bearings seemingly roll uphill as if attracted by magnets of some kind. What’s going on? Swipe for reveal as it is truly a matter of perspective. A wonderful take on an illusion invented by Kokichi Sugihara of Meiji University. 3D printed by my good friend @zathras5 (Roger Key) from a file designed by Julian Hardy. 

The Physics of Tippe-Top Inversion

Get a nice tippe-top from this fine source: 

From Etsy: BUY NOW Flip Over Tops

Physics of Tippe-Top Inversion: spinning things often have surprising physics! In brief: friction with the surface provides a torque that acts on the existing angular momentum of the top to flip it over. The top will stay flipped until the spin rate slows down enough to where its center of mass pulls it back to the resting position. Inversion phase shown at 240fps- note the little hop the top takes as it goes on to its stem! 

Phenakistiscope Spinner Set

Get these amazing spinners from aPyroDesign;

From Etsy: BUY NOW: Animation Spinners

Phénakisticope Spinner Set: two spinners- one a laser cut and printed acrylic with a set of images similar to the animation design of a flip book (but in a repeating cycle)- and the second a black disk with thin slit openings. Spin them in opposite directions and then look through the black disk at the first to reveal an animated image, in this case a running stick person. The effect looks better in person in that the frame rate of the video capture process adds some artifacts. Using the second black disk like this turns the spinners into a phenakistiscope, the 1833 invention that started moving media animation that lead to the development of movies and video. Under very bright light the animation can also be seen using a smartphone camera in video mode, but the black disk allows one to see the animation without such technology.