The eighth annual US Invitational Young Physicists Tournament was held Friday and Saturday, January 29-30, at Randolph College in Lynchburg, VA. Eleven teams from around the world competed. Phoenixville Area High School of Pennsylvania was atop the standings after the six preliminary rounds. In the final rounds, Shenzhen Middle School, of Shenzhen, China, earned the championship trophy.

• Dates

  Sunday, January 29 - Monday, January 30

• Host Institution

  Randolph College

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.

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.

Transformer Impedance Reflection

A YouTube video titled “Transformers – Experiments and Demos” 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.

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.

Champions: Shenzhen Middle School
Second Place: Rye Country Day School
Finalists: The Harker School, California; Phoenixville Area High School
Clifford Swartz Poster Session Champions: Nanjing Foreign Language School