### Elastic Equilibrium Puzzle

Get this puzzle here:

From Amazon: **BUY NOW: Atomic Cherry Puzzle**

Elastic Equilibrium Puzzle: six spheres held together by three plastic springs. When assembled each sphere exerts the same force on its four neighboring spheres, producing this equilibrium state only if all six spheres are used to balance all the forces. A fun configuration to analyze in a 1st year physics course- the Atomic Cherry by Brainwright puzzles.

### Sphere Sticks Geometric Puzzle

Get this affordable and amazing puzzle here:

From Etsy: **BUY NOW: Sphere Sticks**

Sphere Sticks Puzzle: 30 identical wood pieces, each with two notches as shown, can create 12 interlocking pentagons in a perfect symmetry- look carefully and you can see that each rod is in an identical configuration with the 4 others that connect with it. Precision cut notches on the rods allow them to interlock with elastic tension such that vector sum of the 4 forces sum to zero in this tensegrity type equilibrium. The dodecahedron, with its 30 edges and 12 sides, is the basis of this puzzle sculpture.

### Soma and Rhoma Puzzles

The Rhoma Cube is a vintage item and can sometimes be found on eBay:

From eBay: **Search NOW: Rhoma and Soma Puzzles**

Soma Cubes are available in a wide viariety:

From Amazon: **BUY NOW: Soma Cube**

From Etsy: **BUY NOW: Soma Cube**

SOMA and RHOMA Puzzles: Replace every cube in the Soma puzzle with a rhombohedron to create the Rhoma puzzle- where the seven slanted pieces now make a larger rhombohedron. Here I’ve painted the corresponding Soma and Rhoma pieces to match on these sister puzzles that share identical edge lengths. While there are 240 ways to make the larger cube from the 7 Soma pieces, there is only one solution for the 7 Rhoma pieces. The original Soma Cube is a math toy has an interesting connection to physics- invented by Danish scientist and artist Piet Hein who claimed that this puzzle idea came to him as he was listening to a lecture on Quantum Mechanics by Werner Heisenberg in 1933. The seven pieces are all the ways 3 or 4 cubes can be joined, such that each piece has at least one inside corner.

### Impossible Bottle with Arrow

Get an impossibe object from this artist here:

From Etsy: **BUY NOW: Impossible Bottles and Objects**

Impossible Bottle with Arrow Sculpture Puzzle: a new seemingly impossible object in my collection- Created with clever engineering, this “impossible” syrup bottle contains a wooden arrow that should not fit through its neck. The wood of the arrow is notably one uncut piece, and yet a metal washer is also somehow trapped on the shaft of the arrow. The puzzle aspect is to consider how the bottle was produced (I personally have some theories- but I do not know the secrets of this artist). I can tell you with high certainty that the bottle was never cut or altered in anyway, and it was not somehow formed around the objects. This bottle by Brad Byers is an expertly crated example of the impossible object genre.

### Cone of Apollonius

Similar models available here:

From Etsy: **BUY NOW: Cone of Apollonius**

Cone of Apollonius: Slicing a cone with a plane will produce the famous curves known as the conic sections, as demonstrated with this beautiful vintage wood model by Nasco. Slicing at a right angle to the cone’s axis of symmetry produces a circle, and tilting the intersecting plane a bit produces an ellipse. When the plane is tilted parallel to the side of the cone the curve produced is a parabola, and tilting even further creates a hyperbola. The discovery of the mathematics demonstrated here are attributed to Apollonius of Perga from about 250 BC- thousands of years later Kepler, Newton, and others showed these conic sections to be intricately connected to many branches of physics such as planetary orbits and the optics of telescopes.

### Impossible Knot

Follow the link below for full explanation and instructions.

From mathematician/artist George Hart: Tying the Knot Puzzle

Impossible Knot: how did this overhand knot get into this closed continuous band of rubber? It did not get there by cutting the loop, tying a knot, and rejoining it. Amazingly this band was once a rubber o-ring. How was it cut to produce a knot? An “impossible object” related to the Möbius strip by mathematician and artist George Hart- a brain teaser puzzle he calls “Tying the Knot”.

### Frabjous Geometric Sculpture Puzzle

Get one here- five colors to choose from:

From MoMath: BUY NOW: Frabjous Sculpture Puzzle

Frabjous Geometric Sculpture Puzzle: 30 identical laser cut acrylic pieces interlock into 12 interconnected five point stars (each with a spiral vortex center) in this puzzle based of the Frabjous sculpture by artist and professor of mathematics George Hart (Prof. Hart is now on Instagram, follow him at @george.hart.sculptor to see more of his amazing work.) Note that if one connects the tips of the stars one gets the outline of a dodecahedron, with its 30 edges and 12 sides, and if one considers the face planes of the linked pentagrams the underlying shape is a polyhedron called the “great rhombic triacontahedron”. A year or so ago I got to visit the National Museum of Mathematics in NYC where I bought this puzzle in the @momath1 museum shop. This puzzle was great fun to assemble- buy one to support this inspirational museum, and make a great sculpture for your bookshelf!

### Rhombic Blocks Mathematical Puzzle

This beautifully made puzzle available here::

From Etsy: **BUY NOW Rhombic Blocks **

Rhombic Blocks Mathematical Puzzle: There are 9 possible ways three rhombuses can be joined together along a common edge, and similar to pentominoes, these 9 tri-rhombs can tile a polyhedron, in this case a hexagon. There are 14 solutions to this puzzle, and one where no same-colored pieces touch. A beautiful math discovery by puzzle master Stuart Coffin.

### Repelling Marbles Puzzle

Get this affordable and fun kit here:

From Educational Innovations:** BUY NOW Mystery Marbles Puzzle Kit **

Mystery Marbles Puzzle: a physics brain teaser (now available as a kit) what's going on here? Three glass marbles can move but stay separated in this liquid filled tube no matter the orientation- why do they not touch? Swipe for reveal of components.

**See also: Poly-acrylamide Polymer Vanishing Act**

### Pythagorean Puzzle

Available here:

From Creative Crafthouse:** BUY NOW Pythagorean Puzzle**

Pythagorean Puzzle: a proof, in physical form, of one of the most famous equations concerning the sides of any right triangle. The area of a square with side c of the hypotenuse is indeed equal to the sum of the areas of the squares of side a and b. This kit also allows at least two other ways to prove this theorem named after the famous Greek mathematician from 500 BC. One of the most used formulas when calculating vectors in physics classes ?

### Missing Edge Piece Puzzle

Get this puzzle here:

From Etsy: **BUY NOW: Missing Edge Puzzle Card**

See the simiar and amazing:** Matsuyama's Puzzle**

Missing Edge Piece Puzzle: fun math involved in the design of this puzzle, which illustrates how the concept of area can challenge our intuitions. Swipe to see the similar and amazing Matsuyama’s Paradox puzzle. A precision crafted puzzle by Jeux Efcé game shop.

### Pearl Vault Puzzle

Get this puzzle here:

From Etsy: **BUY NOW: Pearl Vault Puzzle**

Pearl Vault Puzzle: a tetrahedron assembly of four identical pieces traps within a pearl. Three challenge aspects to this puzzle: 1) get the pearl out from the center, 2) explain the physics of how the disassembly occurs, and 3) reassemble- for which 3) might be the most challenging. Swipe for reveal and note the conservation of momentum aspect of the solution. Designed by Bruce Patterson and expertly produced by Pyrigan Puzzles.

### Impossible Nail

Nice versions are curretnly available from Etsy:

From Etsy: **BUY NOW: Impossible Nail**

Impossible Nail: An eighteen-penny nail driven through the inner notches of a solid piece of wood. The wood was notched and the nail added- no glue used or cuts made, and the nail is solid and in one piece. Not impossible, but creating this does depend on the use of some amazing physical properties of wood. I won’t reveal the method here but a quick search on YouTube produces a few how-to videos showing the process.

### Impossible Threads

Available here:

From Crux: **BUY NOW: Impossible Threads **

Impossible Threads: a classic project for learning machinist skills on a metal lathe where threads are made in the middle of a rod with solid ends- how then where the nuts placed on the threads? The ends are indeed the same piece of metal and where never detached. Swipe to reveal the method that takes advantage of how precisely metal can be machined.

### Bubble Trouble Puzzle

This hard to find puzzle is sometimes found here:

From magicorum.com: **Bubble Puzzle**

See more physics puzzles: **featured physics puzzles**

Bubble Trouble Puzzle: physics brain teaser- the trick here is to move all air bubbles to the center bulb. As with all puzzles featured here on @physicsfun, the solution relies on some fun basic physics principles- can you figure out which ones? Swipe to reveal solution.

### Reverse Cartesian Diver

Glass divers available here:

From Amazon:** BUY NOW Glass Divers **

The reverse diver needs a bottle with a oval shaped cross section. I used the bottle from this product- it has the right shape and size and the label comes off easily:

From Amazon:** BUY NOW Oval Shaped Bottle Source **

Inexpensive and fun diver kits available here:

From Educational Innovations: **BUY NOW Cartesian Diver Kits **

Wikipedia has the details on the Cartesian diver (and reverse diver).

Reverse Cartesian Diver: physics puzzle (swipe for hint). On the left is a Cartesian diver- pressing on the bottle forces water into the glass diver, which then compresses the bubble in diver’s head allowing it to sink. On the right is a reverse Cartesian diver- again the bottle is pinched but this time the diver ascends- why?

### Square Dissection Puzzles

Get these and other well made disection puzzles here:

From Etsy: **BUY NOW: Square Dissection Puzzles**

These puzzles are expertly laser cut and sold by GamesEfce. I spray-painted the pieces of mine to better show the shapes and relationships for the video.

Square Dissection Puzzles: a square can be cut (dissected) into polygons and then reassembled into other regular polygons. Shown here: an equilateral triangle, a pentagon, and a hexagon. These are the record holders for smallest number of pieces needed: triangle (4 pieces by Henry Dudeney 1902), hexagon (5 pieces Paul Busschop 1870s) and pentagon (6 pieces Robert Brodie 1891). Fun fact- It is not known if any of these records are the smallest possible, no mathematical proofs yet exist on this question.

### Ice Melt Demo

Get this similar demonstration kit here:

From Amazon: ** BUY NOW Ice Blocks Melt Demo **

Ice Melt Demonstration: Wood or Aluminum- which will melt the ice fastest and why? Both blocks start at the same temperature (room temp) and have the same shape and volume. Swipe to reveal result shown in real time (not sped up!) Hint: Although both blocks are at the same temperature, the aluminum feels cool to the touch and the wood block feels warm. Those who have taken basic physics should have an advantage on this question- one block is an excellent insulator and the other a conductor.