Build-it, Leave-it, Teach-it

For the Build-it, Leave-it, Teach-it (BLT) project, SUNY Geneseo faculty and physics majors build physics demonstration equipment and discuss the best ways to present the demonstration in a classroom.  Physics teacher candidates then bring the piece of equipment to a local high school physics classroom and use it to teach a physical concept to the students.  The BLT unit is then left as a donation to that classroom.


BLT - The Race

In the Fall of 2011, we built "The Race".  In this demonstration, two identical steel balls are released from the same height on two vee-channel tracks.  They accelerate down identical slopes.  Then one ball goes uphill and downhill while the other ball goes downhill then uphill.  Which ball will reach the end of the track first?

(Click on the images below to see an enlarged version.)

BLT - The RaceBLT Oct2011 small










Construction notes


BLT - Lenz's Law

In the Spring of 2012, we presented a "Lenz's Law" demonstration.  In this demonstration, a cylindrical magnet is dropped down a vertical copper pipe and a vertical plastic pipe of identical lengths.  The time of travel is much longer because of the Lenz's Law effect.

   Construction notes  Magnets (K&J Magnetics - D4X0-ND), copper pipe (McMaster-Carr 50475k22), acrylic pipe (McMaster-Carr 8532K13)  Cost per unit less than $20.


BLT - The Falling Slinky

In the Fall of 2012 we presented the "Falling Slinky" demonstration, in which a slinky is dangled from the top and students are asked to predict who it will fall.  In this case a response worksheet and a video were developed to help with the presentation, and data where collected to investigate how the requirement for a written prediction affected students' understanding.

Here's a nice resource:

BLT - Faraday's Jump Rope

 In the Spring of 2013 we presented the "Faraday's Jump Rope" demonstration.  25-foot length of six-conductor wire was configured into a loop with six turns.  The two ends of the loop were attached to a micro-amp galvanometer. 

construction notes

Leads - alligator to bananaOmnimodels HCAP0108$3.99
GalvanometerWards16V 0537$16.50
Terminal BlockMcMaster Carr7527K46$2.76

terminal block wiring

Thermostat Cable (6-lead)McMaster Carr70985k75$11.50 ($0.23 per foot)
Unit price$34.75

BLT - Gauss Accelerator

The Gauss Accelerator is the BLT for the Fall 2013 semester.  This demonstrates the surprising results of the conservation of energy and momentum for collisions between a metal ball bearing (BB) and a powerful magnet.  Each unit consists of:

aone 32" long v-channel (McMaster Carr, 8982K541) resting on wooden blocks  $2.29 each

one Gauss Rifle kit (, $31.54 each)

Some electrical tape to secure the magnets to the v-channel at the positions 4 inches, 12 inches, 20 inches, and 28 inches.

BLT - Poisson Dot

The Poisson Dot BLT was presented in Spring 2014.  This demonstration is based on a historical event that illustrated the wave nature of light.  A green laser pointer ( $13.95 for tw0) was mounted so that the momentary contact switch was pressed on by a clothspin, which also mounted held the laser pointer in place.  A lens (, #56451081 $10.35 each) was mounted into a rubber stopper with a #7 hole, mounted on the front of the laser pointer to expand the beam.  A standard BB ball bearing was glued to a microscope slide and also held with a clothspin on a table a distance away, where the diameter of the laser beam was slightly larger than that of the BB.  The poisson dot pattern appears on a distant wall.  For fun, we had the students read a SCRIPT describing this phenomenon.

Poisson DotDSC 0984small

Poisson DotDSC 0987small

BLT - The Tense Pendulum

This is the Fall 2014/Spring 2015 BLT.  A Spring balance (, $26 Each) hangs on a pivot point and a weight (a water bottle filled with sand) is connected to the spring balance by a long (~1.5 m) string.  At rest the spring balance provides the weight of the water bottle.  When the water bottle is swinging, what will happen to the reading on the spring scale?


BLT - The Hinged Board

The Fall 2015 BLT is the Hinged Board.  A metal sphere sits on a golf tee on a board at a 30 degree angle.  When the board is released, it rotates about one end, and the viewer is supposed to predict which cup the ball will land in.

(Hinges - McMaster Carr 1494A12 - $6.67 each)  (#12 screws McMaster Carr 90294A294 $11.08 for 50)

BLT - Air Lens

Tha Spring 2016 BLT is the Air Lens.  Florence flask is inside a clear plastic box.  Water is placed in the flask and a laser is used to show that parallel rays of light converge.  When water is placed in the box and the flask is filled with air, parallel rays of light diverge.  This enhances understanding os Snell's Law.