Code Number: 1C20.10
Demo Title: Free-Fall in a Vacuum (Penny and Feather Demo)
Condition: Good
Principle: Acceleration Due to Earth's Gravity is Constant
Area of Study: Mechanics
Equipment:
Permanent Penny and Feather Unit, Vacuum Tube with Feather & Penny, Vacuum Pump, Book, and Piece of Paper.
Procedure:
Pop the top off the large Plexiglas tube and reposition the shelf, then carefully place the ball and feather onto the shelf. Place the top back onto the tube. Evacuate the tube which should be able to hold the vacuum for times much longer that a class period. When ready, cut the photogate with your hand which will trigger the shelf to drop and release the ball and feather.
The vacuum tube may have to be taken apart for cleaning. Check the oil in the vacuum pump and maintain at the proper level. Using the triangular variable wedge will help ensure that the tube will not roll off the table.
A small ball of cotton may be substituted for the feather.
A way to do this without the vacuum system is to take a large textbook and place a piece of paper directly on top of it. When this is dropped the paper will drop at the same speed as the textbook and stay directly on top of the book.
References:
- Hollis Williams, "A High-Speed Test of the Equivalence Principle", TPT, Vol. 60, #7, Oct. 2022, p. 594.
- Elida de Obaldia, Norma Miller, Fred Wittel, George Jaimison, and Kendra Wallis, "Bridging the Conceptual Gap Between Free Fall and Drag-Dominated Regimes", TPT, Vol. 54, #4, Apr. 2016, p. 233.
- Christopher L. Vaughan and Moshe Nissan, "Teaching Mechanics with a Digital Camera", TPT, Vol. 25, #7, Oct. 1987, p. 445.
- "M-088: Coin and Feather in Tube", DICK and RAE Physics Demo Notebook.
- George M. Hopkins, "Falling Bodies--Inclined Plane--The Pendulum", Experimental Science, p. 38.
- Julien Clinton Sprott, "1.1, Guinea and Feather Tube", Physics Demonstrations, ISBN 0-299-21580-6, p. 2.
- John Henry Pepper and Henry George Hine, "Gravitation", The Boy's Playbook of Science, p. 14.
- "The Paradox of the Falling Bodies", The Boy Scientist.
- Ron Hipschman, "Falling Feather", Exploratorium Cookbook III, p. 137-1.
- "Falling Feather", The Exploratorium Science Snackbook, p. 50-1.
- Christopher P. Jargodzki and Franklin Potter, "397. Was Galileo Right?", Mad About Physics, p. 154, 297.
- Borislaw Bilash II and David Maiullo, "Falling Together", A Demo a Day: A Year of Physics Demonstrations, p. 27.
- "This Month in Physics History", APS News, Vol. 26, #2, Feb. 2017, p. 2 - 3.
- Borislaw Bilash II, “Falling Together“, A Demo A Day – A Year of Physical Science Demonstrations, p. 238.
"Guinea and Feather Tube", Pike's Illustrated Catalogue of Scientific & Medical Instruments, 1984, p. 207.
A video of the Apollo 15 Astronauts performing this experiment on the moon is available at: