All physicsfun toys

Magic Sake Cup

These are hard to find-- 
also beware that some versions of this cup (Dragonware) contain images many would consider "adult content"! 

I recommend making one with a shot glass and a marble as described in this fun collection of DIY science experiments by Martin Gardner: 
From Amazon: BUY NOW Science Fun by Martin Gardner

Magic Sake Cup: when this antique ceramic sakasuki is filled with clear liquid an image of a bride is revealed! The spherical glass lens at the bottom has a very long focal length in air, but when immersed in water the glass marble has the same focal length as a magnifying glass, unveiling the portrait. Refraction depends heavily on the refractive index of the two transparent mediums. 

Wild Eyes Holographic Glasses

Made by American Paper Optics Inc. All versions of these holographic glasses can be found here: 
from Amazon: BUY NOW Wild Eyes 3D Glasses 

Here is a good description of the physics and principles of operation of these far-field holograms by the manufacturer HoloSpex, Inc. 

Need a laser pointer? Incredibly, you can get 3 (one of each color) for under $10 (including S&H): 
From eBay: BUY NOW Red+Green+Purple Laser Pointer

Wild Eyes Holographic Glasses: put on these goggles and on top of every point-source of light will appear an animated holographic image of sharks swimming. (Here I used a Maglite flashlight with the cap removed.) The "lenses" in these glasses are actually transmission holograms with the image located at the farthest point in the depth of field. In this version there are three holographic images in a trifocal glasses arrangement- tilting one's head brings the animation to life! Holographic glasses can also be used to project an image using the beam of a laser- the very same technology used to make the "projection caps" on inexpensive laser pointers. Made by American Paper Optics LLC.

 

UV Fluid Flow Kaleidoscope

Many versions of this kaleidoscope are available: 
From Amazon: BUY NOW Fluid Flow Kaleidoscope 

From eBay: Fluid Flow Kaleidoscope

UV Fluid Flow Kaleidoscope: original glitter wand kaleidoscope made by Illusions back in the 1990s. Intricate geometry from multiple reflections coupled with the viscous fluid motion of the glitter produces this psychedelic kinetic art. Under the illumination of a UV light this version takes it to the next level featuring fluorescent pieces and phosphorescent stars in the fluid of the wand. 


CMYK Coasters

These coasters are almost sold out everywhere: only The Mona Lisa is still in stock: 
From Amazon: BUY NOW CMYK Coasters 
From eBay: BUY NOW CMYK coasters 

The CMYK model and colorspace on Wikipedia. 

CMYK Coasters: physics and psychophysics of four color printing demonstrated with acrylic slides that assemble to reveal Vermeer's "Girl with a Pearl Earring". Cyan, magenta, yellow, and black (key) comprise the elements of the subtractive color model used in most color printing. Repost of the “most liked” post of 2016!

Pin-Tumbler Lock

One of many amazing and accurate models made by Theodore Gray: 
From MechanicalGifs.com: BUY NOW Pin-Tumbler Lock Acrylic Model Kit 

Pin-Tumbler Lock: simple and accurate model of how a basic lock works. The pins (orange/green) are held in place with springs and keep the tumbler from sliding and releasing the chain. The contour cut into the edge of the key must match the lengths of the green parts of the pins. When the key is inserted, the edges of the green pins line up allowing the tumbler to slide, unlocking the chain. In most locks the tumbler rotates instead of sliding, but the principle is the same. One of many “Transparently Obvious” models in the Mechanical Gifs series created by Theodore Gray. 

Cartesian Diver

Get one here! 
From Amazon: BUY NOW Cartesian Divers 

Cartesian Diver: increasing pressure on the water compresses the air bubble in the small plastic vial (here in the shape of an octopus' head) filling it further with water and making the diver sink. Pascal's principle states that any change in pressure on an enclosed fluid (such as squeezing the plastic bottle) is transmitted evenly to every part of the fluid- the physics of hydraulic brakes! The physics here is great- but the biology is questionable: it's not clear why an octopus would need mask and snorkel! 


Balance Jet

The jet toy in the video is vintage from the 90's and can occasionally be found on eBay. Follow the links after the following video for currently available (and amazing) toys that operate on the same physics principle. 
From eBay: BUY NOW Balancing Jet Toy

Balance Jet: weights in the wing tips create a center of mass below the balance point on the rear of the toy plane- making the system in stable equilibrium on the end of the eraser on the pencil. No magnets! -and yet it can wobble and spin without falling off. Next- since we know the center of mass is under that point of contact, the toy jet can then balance on a pencil in a state of unstable equilibrium. 

RIZE Spinning Ferrofluid Display

Ferrofluid display cells available in a variety of colors: 
From Amazon: BUY NOW RIZE Ferrofluid Interactive Scuplture 

RIZE Spinning Ferrofluid Display: by @mtrdesigns - a colloidal ferromagnetic liquid forms a spiked helix around the threads of a steel bolt in this kinetic sculpture. The bolt contains ferromagnetic iron which channels the field from the strong neodymium magnet in the base and focuses it into the spiral configuration. The curious spiking behavior results from the interplay between magnetic force and surface tension between the liquids.?Special thanks to Matt of MTR Designs studio for this beautiful interactive display.

Splat Pig Ball

Available in many colors and shapes: 
From Amazon: BUY NOW Splat Pig 

Splat Pig Ball: water filled ball made of an extremely elastic and sticky (tacky) soft polymer. This toy can regain its initial shape after extraordinary deformation- as caught in 240 fps slow motion (see the replay). The exact chemical makeup of these splat toys seems to be a trade secret but involves the following main constituents: polymerizing styrene, butadiene napthenic oil, calcium carbonate, and hydrogenated polyterpene resin as a tackifier that allows the temporary adhesion to the surface. Similar polymers are used in toys such as wall tumblers and sticky hands.


Center of Mass Spinning Top

Available here 
From DaWanda: Magneto Gyro by Kreisel 

Center of Mass Spinning Top: any 2D shape will spin nicely if spun about an axis through its center of mass. Careful placement of stem (held in place by neodymium magnets) allows the half disk of this acrylic protractor to spin evenly. If the placement is off by even a millimeter the top will not balance. Thanks to Tim Rowett for sending me this unusual top.

Bismuth Crystal Pendent

See more of Ernie's amazing creations here in his Etsy shop Element83 
From Etsy: BUY NOW Bismuth Jewelry

Bismuth Crystal Pendent: element 83 on the periodic table, bismuth becomes crystalline when melted and cooled. Reaction with air creates oxide coatings that provide the amazing Iridescent hues of yellow and blue long associated with bismuth. This piece of bismuth geode was set into a silver bezel by jeweler and artist Ernie McElhannon. 


Thaumatrope

Get a set here: 
From eBay: BUY NOW Thaumatropes 

Wikipedia has some good details on the history and operation of the Thamatrope 

Thaumatrope: the physics and psychophysics of vision in this reproduction of a toy invented in 1824. Still images flashed in rapid succession produces the the combined image of bird + cage through persistence of vision. When the image flash rate is above the flicker fusion frequency (approximately 16Hz) we perceive fluid motion- the basis for all movies and TV. ?Thanks to @artofplay for sending me this nice reproduction!

Photoelastic Polymer Toys

Glitterins offers toys for young children that utilize the physics of polarization: 
From Glitterins: Polarizing toys

Photoelastic Polymer Toys: a simple polariscope designed for kids. Special gel polymer cutouts (this one in the shape of an eye) show how polarized light will reveal internal stresses with bursts of colorful light as the polymer is stretched and compressed. ?Special thanks to Pamela Saha of Glitterins for sending me this wonderful kit.


Scale Jupiter and Earth

Made by Jay Fisher and available here! 
From Shapeways: BUY NOW Jupiter 

Or buy the Solar System! 
From Shapeways: BUY NOW Scale Model Solar System

Scale Jupiter and Earth: 3D printed accurate scale model of the Earth (diameter = 0.80 cm) and Jupiter (diameter = 9.0 cm). Wonderful detail allowed by the 3D printing process reproduces the belting and storms in the Jovian atmosphere- note that the hundreds year old cyclone that is the Great Red Spot is more than twice the size of our home planet. Made by artist/maker Jay Fisher using images from NASA. More planets to come.

Mystery Orbiter UFO

Similar toys available here: 
From Amazon: BUY NOW Gravitron Gyroscope UFO 

From eBay: BUY NOW Gravitron Space Gyroscope

Mystery Orbiter UFO: hidden within this flying saucer shaped toy is a gyroscope, allowing it to balance at seemingly impossible angles, and causing it to precess around an axis through the contact point. The physics and vector nature of angular momentum! Blowing air through one of the three holes spins this gyroscope up.