For this demonstration stronger magnets work best:
From Amazon: BUY NOW: Neodymium Magnets
Here is a good small turntable with bearings:
From Amazon: BUY NOW: Spinning Base
Magnetic Influence on Aluminum: physics puzzler- spin a magnet under a beer can suspended by a thread, and the can will turn. Why? Aluminum is not ferromagnetic, and as shown, magnets are not attracted to the can. So how does a spinning magnet influence the can to spin?
Answer: the can spins due to eddy currents induced in the conducting aluminum due to the moving magnetic fields underneath. The eddy currents make the can into a temporary electromagnet that then interacts with the magnets below according to the famous law by Lenz.
This inexpensive kit available here: From eBay: BUY NOW
Hyperbolic Holes Kit
Hyperbolic Holes: a straight rod, in this case a pencil, glides through a symmetrical pair of curved holes. The design is based on the hyperboloid, the 3D ruled surface traced by an offset rotating diagonal line. This device is sold as an inexpensive kit to assemble yourself, and includes a motor with geared drive and pre-cut pieces. The pencil is my addition- just the right size to clear the curved openings.
The DIY version can be assemebled with these parts. Steel wire of guage 10 or 12 should work well.
From Amazon: BUY NOW: Quilting Hoop, Neodyumium Magnet, Steel Wire
Magnetic Hoops Suspension Sculpture: Steel circles are suspended by a magnet (black sphere) and held down to the base by a thin thread. The tops of the steel hoops, being ferromagnetic, become a north pole in the presence of the south pole end of the black magnet, so they are attracted to the black magnet, but repel each other. Made by Rathcon Inc. in 1970. Swipe to see my DIY version made from a quilting hoop, neodymium magnets, and some bailing wire.
Get this easy to assemble kit here:
From Educational Innovations: BUY NOW Simplest Motor Kit
Electric Motor: in its simplest form!- coil, magnet, and battery. The wire of the coil has an insulating coating- and this coating is carefully scrapped off one side on each end. When current passes through the coil it becomes an electromagnet and the permanent magnet repels it making it spin- as it turns the currents goes on and off depending if the copper posts are in contact with the bare wire (current on) or the still insulated wire (current off). I have motors with fewer parts- but they operate on more complex principles.
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!
Just thread a rubber band through two of these drilled steel balls and you are ready to go!
From Amazon: BUY NOW
Centripetal Spheres: two ball bearings connected by a rubber band orbit each other as energy oscillates between elastic potential energy and rotation kinetic energy. Just wind up the rubber band and let go. When the rubber band has unwound the rotational inertia of the bearings winds it back up until it changes direction. The process repeats until the initial energy is dissipated through friction.
Amazon lists acrylic tubing at a reasonable price: get a 2 foot long tube with an inner diameter of 1.5 inches for about $17 US. This will accommodate a large marble for the demonstration.
From Amazon: BUY NOW Acrylic Tubing
For a 1.5 inch inner diameter (3.8 cm) tube you will need a 10 inch (25.4 cm) wide sheet to complete a cylinder inside the tube.
From Educational Innovations: BUY NOW Polarizing Film
Polarizing Filter Black Wall Illusion: two sheets of polarizing film (with polarization axes oriented at 90 degrees to each other) create this illusion inside an acrylic tube. Physics magic!
These aluminium 1 Yen coins are the perfect denisty to float as shown in the video:
From Etsy: BUY NOW: 1-Yen Coins (20)
Floating Yen: the surface tension of water is strong enough to suspend the aluminum coin, and a trapped column of air in a second glass can submerge a portion of the surface with the coin. The 1-Yen coin has just the right mass and density for this demonstration. One of my favorite DIY physics demonstrations.
Get a set here:
From eBay:(best selecton) BUY NOW Ring Chain Catch
From Amazon: BUY NOW Ring and Chain Set
The physics of this trick in great detail with more slow motion: Ring Falling into a Chain: No Magic — Just Physics
Ring Catch Chain Trick: a solid ring will be caught by a loop of chain if it tumbles during its fall. By Newton's Third law, when the ring twists into and hits the chain, the impact transfers momentum to the end of the chain, which rises up and over the ring- seen here in 480 fps slow motion.
The bottle used here is from Voss Water: a nice cylinder and the labels come off easily. Amazon has the ingedients:
From Amazon: BUY NOW
acetone, blue glitter, food coloring, Voss Water
The density column I made for this video is based on blend of two ideas: this "science snack" from the exploratorium: Klutz-Proof Density Column and this ChemED X post: Blog of Prof. Tom Kuntzleman
See my Salt Fractionation post for details.
Unmixing Density Column: three liquids that won’t stay mixed! Acetone (dyed blue) floats on top of the higher density vegetable oil, which in turn floats atop salt water (dyed orange) which is more dense than oil. Acetone usually dissolves in water through hydrogen bonding interactions, but solubility can be altered. In a process called “salting out” a sufficient amount of salt is dissolved such that the water molecules, which are much more attracted to the resulting Na+ and Cl- ions (through ion-dipole bonds), will then ignore the weaker acetone hydrogen bonds. This results in the spontaneous separation of these three liquids no matter how well shaken up.
Guage block sets can be a bit pricy, but some fairly inexpensive pieces and small sets can be found for demonstrations and such:
From Amazon: BUY NOW: Gauge Blocks
Wikipedia has a nice description of Gauge Blocks and the Phenomenon of Wringing
Wringing Gauge Blocks: two blocks of metal (not magnets!) will stick together by a process called wringing if their surfaces are flat to high precision- such as these gauge blocks found in most machine shops. Here two blocks are forced apart with a snap, and then wrung back together with the characteristic sliding motion technique. Gauge blocks are flat to less that one millionth of a meter and are used by machinists for precision length measurements and calibration. The science of the wring force remains somewhat a mystery and no one has yet found a fully excepted physics description- but we do know that blocks will wring in a vacuum and that the force can be up to 30 times that of weight of the blocks. Fun physics from the shop!
Amazingly this motor is available for less than $10 US.
From Amazon: BUY NOW: Brushless Motor/Generator with LED
Electric Motor/Generator: this inexpensive and common motor can also serve as a generator of AC electricity- here lightning an LED when the shaft of the rotor is spun by hand. Most electrical energy we use today is produced by moving a magnet near a coil of wire (known as Faraday’s law of induction) to produce an electric current. Removing the permanent magnet casing reveals this design to use 9 separate copper windings. I made a transparent second rotor with six neodymium magnets- and when these magnets are made to move near the windings the LED again lights with the flow of current. Swipe to see the beautiful magnetic field pattern of the rotor design using magneview film.
This DIY magneits sculpture can be assemebled with these parts. Bring a magnet into a craft shop to find some necklace chain that is non-magnetic.
From Amazon/eBay: BUY NOW: Quilting Hoop, Neodyumium Sphere Magnets
Magnetic Suspension Sculpture: two neodymium magnets on chains suspended by their mutual magnetic attraction in this prototype kinetic sculpture. These powerful magnets hold the chains taut with about a 2cm gap. Made from a quilting hoop where the magnets connect under their own force to steel nails soldered on to non-magnetic chain.
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!
Glass divers available here:
From Amazon: BUY NOW Glass Divers or this complete set Cartesian Diver Kit
Inexpensive and fun diver kits to make in a bottle available here:
From Educational Innovations: BUY NOW Cartesian Diver Kits
Cartesian Divers: increasing pressure on the water compresses the air bubbles in the small glass vials filling them further with water making them sink. Pascal's principle states that any change in pressure on an enclosed fluid (such as pushing on the rubber cover) is transmitted evenly to every part of the fluid- the physics of hydraulic brakes! Named after the physicist and philosopher Rene Descartes.
The Actuator mechanism is out of production but can still be found on eBay, comes with power supply, Expandagon kit, and connecotors that snap on to a Hoberman Spjere.
From eBay: BUY NOW: Hoberman Actuator
The spheres are still in production and come in various sizes and colors:
From Amazon: BUY NOW Hoberman Spheres
Hoberman Actuator with Sphere: This actuator mechanism creates kinetic art out of a Hoberman sphere, designed to smoothly expand and contract the isokinentic structure. The Hoberman sphere itself is a special assembly of foldable linkages consisting of rigid bars and simple hinges is kinematically over constrained- motion can only occur along the radial direction and the movement of any hinge creates motion in all the joints. The engineering and physics behind deployable space structures!
All the ingredients are available from your local market/drugstore. The trick is to find a dye that works for acetone, but will not color water- believe it on not blue glitter will color the acetone nicely and not change the salt water. Follow this link for details:
ChemEd X: Blog of Prof. Tom Kuntzleman
Of course Amazon has what you will need:
From Amazon: BUY NOW
acetone, blue glitter, food coloring, cool bottle
Salt Fractionation: two liquids that won’t stay mixed! Acetone (dyed blue) floats on top of the higher density salt water (dyed orange). Acetone usually dissolves in water through hydrogen bonding interactions, but solubility can be altered. In a process called “salting out” a sufficient amount of salt is dissolved such that the water molecules, which are much more attracted to the resulting Na+ and Cl- ions (through ion-dipole bonds), will then ignore the weaker acetone hydrogen bonds. This results in the spontaneous separation (shown here in real time) of the liquids no matter how well shaken up.
Here is the NdFeB neodymium magnet used in this video:
From Amazon: BUY NOW: Neodymium Disk Magnet
Please use cuation when handeling strong magnets like this one. Small nails, paperclips, staples and other houlshold object made with iron will interact interestingly with the magnetic feild.
Ferromagnetic Interaction: iron rich nails temporarily become dipole magnets in the presence of an intense magnetic field from a large neodymium super magnet. Here the neodymium disk magnet is set with its north pole pointing up, so the point of each nail becomes a south pole (repelling each other) and the head of each a north pole. Imbued with these temporary induced fields, the nails will try to align themselves with the neodymium dipole’s field like compass needles, and the nails will interact with each other in interesting ways.