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## 02 February 2015

### USIYPT 2015 -- results, and problems for USIYPT 2016!

This past weekend, Woodberry Forest School hosted the 2015 US Invitational Young Physicists Tournament.  Nine schools from around the country and the world participated in "Physics Fights," ritualized discussions about research projects.  The teams included:

The Harker School, CA - CHAMPIONS

Woodberry Forest School, VA - Second Place

Rye Country Day School, NY - Final Four

Renmin University HS, China - Final Four

Nanjing Foreign Language School, China - Swartz Poster Session Champion

Pioneer School of Ariana, Tunisia

Shenzhen Middle School, China

Princeton International School of Math and Science, NJ

Phoenixville Area High School, PA

At the closing ceremony, the trophies are awarded, and then the teams are given their "homework assignment:"  The four problems for USIYPT 2016 were revealed.

In 2016, the tournament will be held Jan. 29-30 at Randolph College in Lynchburg, VA.  Let me know if your school would like an invitation to participate, or if you would like an invitation to judge.  Problems include:

#1 --  Domino Toppling: On 6 August 2014, in Charlotte, North Carolina, a team from Prudential Financial broke the Guinness World Record for toppling the largest domino stone, measuring roughly 30 ft x 15 ft  x 3 ft.  Each domino in the chain had the same aspect ratio of 10:5:1.  Study this phenomenon, then design and construct a domino chain whose overall lateral length before toppling is 3 meters, that starts with a domino stone that you can hold in your hand, and will topple the tallest possible stone. You may change the aspect ratio of your domino stone chain, however all stones must have the same aspect ratio, and all stones must be constructed of the same materials and in the same manner. You must launch the initial, smallest stone with a gentle finger push that topples that stone.

#2 – Blender Lift: If you hold an immersion hand blender's blades under water in a beaker or pot or pail, under certain circumstances you can lift the beaker and the water by lifting only the hand blender as shown in the picture below.  Study this phenomenon for a wide range of the relevant parameters comparing your theory that explains the effect to the experimental results.  Predict the
maximum weight of water and container that your blender can lift and verify this prediction by experiment.

#3 -- Transformer Impedance Reflection: the recently posted YouTube video titled "Transformers – Experiments and Demos" (v=y0WrKT45ZZU) shows a demo at the 4 minute mark.  The demo purports to show that removing a light bulb in the secondary circuit of a transformer will cause a light bulb in series with the primary to turn off, i.e., "a impedance reflection." Analyze this demo and the published explanation of this effect (W. Layton  Transformer Impedance Reflection, The Physics Teacher 52 (7), Oct 2014, p. 426-427).  Provide theoretical and experimental evidence to explain or refute this effect.

#4 -- Bouncing Laser Beam: – a laser will curve and even bounce in a medium whose index of refraction decreases with height.  Although there are several ways to produce this medium, the photo below was created by pouring thick, transparent Karo syrup into a tank and then pouring water on top of the syrup.  Approximately 12 hours later, the bouncing laser beam can be observed.  Create this apparatus or a similar one, study the theory of this effect, and use your results to measure the index of refraction of the medium as a function of height from the bottom of the tank.