2A20.45 - Meniscus - Stable Equilibrium | Instructional Resources and Lecture Demonstrations

Start with the evaporating dish and water. The water should come to about 1" from the top of the evaporating dish to start the experiment.

Add 1 to 3 ping pong balls and notice that they will quickly migrate to the sides of the dish (Concave meniscus).

Adding more water to the evaporating dish until the dish is overfull will cause the ping pong balls to migrate to the center of the dish (Convex meniscus).

Code Number:

2A20.45

Demo Title:

Meniscus - Stable Equilibrium

Condition:

Excellent

Principle:

Concave vs. Convex Meniscus

Area of Study:

Heat & Fluids

Disclaimer

Equipment:

9" evaporating dish, ping pong balls.

Procedure:

Start with the evaporating dish and water. The water should come to about 1" from the top of the evaporating dish to start the experiment. Add 1 to 3 ping pong balls and notice that they will quickly migrate to the sides of the dish (Concave meniscus). Adding more water to the evaporating dish until the dish is overfull will cause the ping pong balls to migrate to the center of the dish (Convex meniscus).

References:

Mohamed Boutinguiza Larosi, "Floating Together on the Top", TPT, Vol. 53, # 2, Feb. 2015, p. 93.
Wojciech Dindorf, "Stable Equilibrium at the Top of a Hill", TPT, Vol. 40, # 2, p. 116, Feb. 2002.
Harold J. Teague, "Position of Objects Floating in a Glass", TPT, Vol. 36, # 7, p. 410, Oct. 1998.
Martin Gardner, "Two Corking Good Challenges", TPT, Vol. 31, # 8, Nov. 1993, p. 477.
George B. Barne, "Divergent Barroom Physics", TPT, Vol. 14, # 1, January 1976, p. 41.
James T. Schreiber, "Barroom Physics, Part II", TPT, Vol. 13, # 7, Oct. 1975, p. 418.
Richard A. Marble, "Floating Objects", TPT, Vol. 10, # 2, Feb. 1972, p. 67.
James T. Schreiber, "Barroom Physics, Part 1". A Potpourri of Physics Teaching Ideas - Fluids and Heat, p. 125.
Martin Gardner, "Two Corking Good Challenges", Science Tricks, p. 13.
Martin Gardner, "Center the Cork", Entertaining Science Experiments with Everyday Objects, p. 117.
Vicki Cobb and Kathy Darling, "Floating Odds", Bet You Can't!, p. 62.
Yves Pomeau and Emmanuel Villermaux, "Two Hundred Years of Capillarity Research", Physics Today, March 2006, p. 39.
Jearl Walker, "2.85, Breakfast Cereal Pulling Together", The Flying Circus of Physics Ed. 2, p. 119.

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