granular convection - 2025 ACF Nationals

Bonus

An explanation of this effect is that if a certain system’s center of mass is not optimally low, then smaller particles tend to move downward. For 10 points each:

[10m] Name this effect in which shaking a container of muesli causes larger particles to rise to the top. It is sometimes named after a food.

ANSWER: granular convection [or Brazil nut effect; prompt on BNE; prompt on convection]

[10h] Granular convection can be explained by using a model named for this physicist to calculate the transverse speed distribution. In granular materials, high values of friction cause pressure to plateau at high depth due to a law that this physicist first observed in corn silos.

ANSWER: H. A. Janssen [accept Janssen model or Janssen’s law]

[10e] Janssen derived his model by assuming that this value was constant. The buoyant force is the product of this quantity, displaced volume, and little g.

ANSWER: mass density [prompt on rho]

Answerlines and category may not exactly match the version played at all sites

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Conversion

Team	Opponent	Part 1	Part 3	Total	Parts
Arizona State	Waterloo B	0	10	10	E
Columbia A	WUSTL B	10	10	20	ME
Florida	Illinois B	10	10	20	ME
Georgia State	Johns Hopkins	0	0	0
Georgia Tech	Toronto A	10	0	10	M
Harvard	Maryland	0	10	10	E
Illinois A	Virginia	10	0	10	M
Iowa State	Indiana	10	0	10	M
MIT	WUSTL A	10	10	20	ME
Minnesota	Michigan	0	10	10	E
Northwestern	Stanford	0	10	10	E
Ohio State	UCF	0	0	0
Ottawa	Cornell A	10	10	20	ME
Penn State	NYU	0	10	10	E
RIT	Toronto C	10	10	20	ME
Texas	North Carolina B	0	10	10	E
Toronto B	Winona State	10	10	20	ME
Vanderbilt	LSE	0	0	0
Waterloo A	North Carolina A	10	10	20	ME
Yale	Cornell B	0	0	0

Summary

Tournament	Exact Match?	Heard	PPB	Easy %	Medium %	Hard %
2025 ACF Nationals	Yes	20	11.50	65%	50%	0%