Time's Up: inverse of the sandglass- tiny plastic beads are less dense than the water and thus ascend to the top of the container under the influence of a buoyant force in accordance with Archimedes' principle. This timer takes almost exactly 6 minutes to complete shown here at normal speed for the first half of this video, and the second half is condensed to 24 seconds in time-lapse.
Get a set here:
From Educational Innovations: BUY NOW Newton's Yoyo
Newton Yo Yo: Newton's 3rd Law states that action force equals opposite reaction force- the the green and yellow spheres have equal mass, so the forces of the collision provide accelerations that are equal and opposite such that the spheres trade places.
Get this set here!
From Etsy: BUY NOW: Dudeney's Dissection 3D Print
Dudeney's Dissection: an equilateral triangle canbe cut (dissected) into four pieces that will then assemble into a square. This 3D printed version comes as a puzzle- fit the pieces in each of two containers- a square and a triangle, which also makes it clear the two supplied shapes are of equal area. Fun fact: It is not known if a similar three piece dissection is possible. Also called Haberdasher's problem and described in 1907 by Henry Dudeney it is the only 4 piece solution known.
Need a laser pointer? Incredibly, you can get 3 (one of each color) for under $20 (including S&H):
From Amazon: BUY NOW Red+Green+Purple Laser Pointer
Rainbow Symphony has a nice selection of diffraction gratings and sun catchers:
From Amazon: BUY NOW: Diffraction Grating Toys
LASER Pointers + Diffraction Grating: three frequencies of laser pointer- Red (635 nm), Green (532 nm), and Blue (450 nm). Note that the distance between the intensity maxima (bright spots) is greatest for the red (long wavelength) and closest for blue (shortest wavelength) with the green in between. The diffraction grating is the same form as one of those rainbow fireworks glasses- this one from has 13500 lines per inch.
Get one here! Make sure to get the Jr. Scientist version of this kit for best results.
From Amazon: BUY NOW Strandbeest Model Kit
Read about Theo Jansen and his novel leg linkage mechanism for the Strandbeests via these Wiki pages.
Strandbeest Mini: A fully working model of artist Theo Jansen's Strandbeest kinetic sculpture which features Jansen's linkage- a unique leg mechanism which converts rotary motion of a crackshaft into smooth walking motion. Jansen's creations are usually a couple meters high and walk the beaches of the Netherlands powered by the wind. This version comes as a model kit that snaps together with no glue- a really fun project!
Get a Back Flip wind-up toy here:
from eBay: BUY NOW: Uglydoll Backflipping Toy
from Amazon: BUY NOW: Backflipping Wind Up Toys
Backflipping Wind Up: an energy transfer toy- a wound coil spring transfers and stores energy through a set of gears to a straight spring which is suddenly released to create kinetic energy which is then converted to gravitational potential energy- sending the toy air bound into a back flip. Here the Uglydoll character Is made of clear plastic allowing the internal mechanism to be visible. In addition the feet of the character must push off with just the right rotation rate to allow for one full rotation in the air, and the tail has a foam pad to absorb the impact and stop the rotation. A lot of fun physics to consider in this toy.
Get one here:
From eBay: BUY NOW: Tail Spin Kinetic Toy
Tail Spin Geared Kinetic Toy: fourteen gears arranged on seven linked segments meshed in such a way that the configuration can roll up and stack compactly or extend into a line. With a flick of the wrist, one can impart enough angular momentum to the assembly to cycle it through its full range of motion- shown also in 240fps slow motion at the end of the video. Invented by Oskar van Deventer and produced by Think Fun toys.
These stickers transition back and forth and can be used on many surfaces. Get some here:
physicsfunshop: BUY NOW: Thermochromic Saftey Sticker
Thermochromic Safety Sticker: the liquid crystal ester dye in this reusable sticker is calibrated to change color when the surface temperature exceeds 50°C (122°F)- that at which prolonged contact (more than 0.5s) will burn skin. Here the safety sticker is attached to a slab of aluminum and heated with a simple candle- it took about 3.5 minutes for the heat to distribute and bring the aluminum to the threshold temperature. When the surface cools the sticker again appears blank and can transition over and over again
Get one here:
From Amazon: BUY NOW Dolphin Timer
Oil Drop Timer with Dolphins: immiscible fluids of different densities stay separate under gravity with the lightest density on top. The density of the plastic dolphins is greater than the density of the top fluid but less than the density of the bottom fluid, so they stay at the boundary in equilibrium. The dolphins have a metal weight in their tails so that the buoyant force will keep them upright even as the liquids trade places (2 minutes shown in time-lapse). Archimedes' Principal at work here at multiple levels.
Small and large drinking birds available here:
From Amazon: BUY NOW: Mini-Drinking Bird Heat Engine
See more drinking birds in my collection
Mini-Drinking Bird Heat Engine: this hummingbird sized heat engine is the latest species added to my drinking bird collection. This little guy comes with the traditional top hat and his own plastic goblet- which is the perfect height for a standard drinking bird to share. Cooling by evaporation at the head leads to lower pressure in the top bulb, the pressure in the bottom bulb pushes the dichloromethane fluid up the neck making the bird top heavy and the bird tips over dipping its beak and letting the fluid return to the bottom bulb. The process repeats, and as long as the top stays wet and cooler than the bottom this heat engine will continue to cycle.
Get this nice example of mystery braid here:
From Art of Play: BUY NOW: Impossible Braid Key Fob
Here is a great video on how to make the mystery braid
See other Impossible Objects in my collection.
Mystery Braid: challenge- how can three strands be braided if both sets of ends are connected? (swipe for reveal) A new addition to my collection of “impossible objects”, this leather key fob is braided from a single piece of leather, constructed by making two parallel slits but not cutting the ends. The solution is well known to those in the field of leatherwork- due to a twist of topology it’s possible to make this braid if the number of left strand over right crossings equals the times the right strand crosses over the left. Four strands braided this way is not mathematically possible, but 3, 5, or any odd number can be done!
I used neodymium disk magnets, small end = 1/2" diameter, Large end = 3/4" diameter.
From eBay: BUY NOW Disk Magnets for Simple Motor
Foil Runner Motor assembly diagram:
Self-Propelled Homopolar Motor on Aluminum Foil Racetrack: A favorite DIY physics toy where disk shaped neodymium magnets supply the static magnetic field for this motor and become the wheels of a very simple vehicle with an AAA battery as the energy source. As soon as both ends make contact with the conducting aluminium foil an electric current will flow which in turn induces a magnetic field underneath the battery assembly. This induced field will then interact with the neodymium magnets on each end causing them to spin- a wonderful example of a motor with minimal components. The racetrack is a cardboard circle from a pizza box covered in kitchen foil.
Similar wine racks available here:
From Amazon: BUY NOW
Balance Wine Rack
Many well crafted versions avaulable here:
From Etsy: BUY NOW
Wine Bottle Balance
Well Balanced Cabernet: a carefully engineered acrylic version of this famous demonstration- the center of mass of the rack/wine bottle system is directly over the base providing unstable equilibrium for this balancing act. Suspended here is Hypothesis by Roots Run Deep, an excellent Napa cabernet sauvignon.
Get this fun cactus lamp here:
From Amazon: BUY NOW: Infinity Cactus Lamp
Infinity Cactus Lamp: parallel partially mirrored panes with green LEDs create the illusion of depth through the physics of reflection and refraction- in the shape of a saguaro!
Get this metallic lava version here:
From Amazon: BUY NOW: Metallic Lava Lamp
From explOratorium store: BUY NOW: Metallic Lava Lamp
See aslo: Magnetic Ferrofluid Lava Lamp
The Lava Lamp: with new pearlescent metallic “lava”- kinetic art with an amazing amount of physics on display: convective heat flow, Archimedes principle, surface tension (note how the smaller blobs form into spheres), and immiscible liquids to name just some of the science behind this famous device. In this loop one can see shock waves ripple through the blobs as they detach, and as they recombine at the bottom. Manufactured by Mathmos and invented in 1963 by Edward Walker of Dorset, England.
Get some of these grow-spheres here:
From Educational Innovations: BUY NOW Growing Spheres
Poly-acrylamide Polymer Vanishing Act: these spheres of hydrophilic polymer have an almost identical index of refraction as that of water- thus when submersed they become invisible. Note the elasticity of these spheres from the way they bounce, while at the same time they refract their surroundings as a spherical lens. The super absorbent spheres start as hard crystals with a radius of 2mm and grow to 11mm when immersed in water. So much physics going on here!