Demonstrations

Free-fall Apparatus

Code Number :	1C30.16
Disclaimer:	Reprinted by permission of Dick Berg, University of Maryland, for use on this website. The demonstrations contained and referenced herein are listed for the purposes of cataloging and describing physics demonstrations which should be conducted only under the direction of a trained instructional support professional or physicist. These demonstrations are not presented for the purpose of being conducted by persons unconnected to this Facility and/or persons not consulting with or being supervised by the recognized instructional support professional or physicist and his/her staff. The University is responsible only for those demonstrations carried out using its own equipment using established safety and scheduling policies, and bears no responsibility for those choosing to use this source material for their own purposes. All demonstrations described and contained herein are public domain, and can also be found in reference materials in libraries, bookstores, and electronic sources. Further information regarding legal liability in use of demonstrations and labs will be found on the web site Injuries in School/College Laboratories in USA. The University of Iowa Disclaimers: U of Iowa Disclaimer All Rights Reserved.
Condition :	Good
Principle :	Measurement of 'g'
Area of Study :	Mechanics
Equipment :	20 V. DC power supply, Electromagnet, Electric timer, Switch pad, Camera, Close-up lenses, Camera power supply, Ball Bearings, Air Track, Timing Gates and Counters, Air Cars, Behr Freefall App., Power Supply (Old Variable Type), Switch, Spark Generator and Spark Tape, laptop and interface, Photogate, picket fence. Videotape of objects thrown of the roof of Van Allen Hall.
Procedure :	Hookup is as shown using the appropriate adapters. For ease of measurement the distance between the ball bearing when it is suspended in the electromagnet and the switch pad should be 1 meter. The screws in the switch pad need to be tightened periodically to insure a good electrical contact. Measurement can also be made by using an inclined Air track and timing the cars through a known distance. The Behr Freefall App. needs to be carefully leveled to insure that the weight will fall at the proper distance from the wire so that good sparking is achieved. Inserting a switch between the power supply and magnet will make it easier to turn of the magnet and allow the weight to fall. Another way to quickly do a measurement of "g" is to drop one of the picket fences through a Photogate. Place a foam pad under the Photogate to prevent damage to the picket fence. The video tape shows a variety of objects being thrown off the roof of Van Allen Hall. The entire 7 story drop is viewed so that you can make measurements if desired. Also, objects are dropped in pairs so that you can see their simultaneous fall.

References

J. A. White, A. Medina, F. L. Roman, and S. Velasco, "A Measurement of g Listening to Falling Balls", TPT, Vol. 45, # 3, March 2007, p. 175.

"Figuring Physics", TPT, Vol. 44, # 8, Nov. 2006, p. 545.

Sebastian M. Torres, Wilson J. Gonzalez-Espada, "Calculating g from Accoustic Doppler Data", TPT, Vol. 44, # 8, Nov. 2006, p. 536.

Pirooz Mohazzabi, "Comments on "Why Do We Feel Weightless in Free Fall?" ", TPT, Vol. 44, # 6, p. 326, Sept. 2006.

Pirooz Mohazzabi, "Why Do We Feel Weightless in Free Fall?" TPT, Vol. 44, # 4, Apr. 2006, p. 240.

Bruce Gregory, "Figuring Inertia and Acceleration", TPT, Vol. 43, # 9, Dec. 2005, p. 566.

Paul Hewitt, "Hewitt's Response", TPT, Vol. 43, # 9, Dec. 2005, p. 566.

Ian Lovatt and Bill Innes, "Resistance Is Not Futile: Air Resistance in an Algebra-Based Course," TPT, Vol. 43, # 8, Nov. 2005, p. 544.

James L. Hunt, "Five Quantitative Physics Experiments (Almost) Without Special Apparatus", TPT, Vol. 43, # 7, Oct. 2005, p. 412.

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Marvin De Jong, "Interfacing Microcomputers: Back to the Future," TPT Vol. 40, # 6, Sept. 2002, p. 360.

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Joseph Gallant and James Carlson, "Long-Distance Free Fall", TPT, Vol. 37, # 3, Mar. 1999, p. 166.

Joseph Gallant, "Errata in Long-Distance Free Fall", TPT, Vol. 37, # 5, May 1999, p. 261.

A. P. French, "Comments on Long-Distance Free Fall", TPT, Vol. 37, # 5, May 1999, p. 261.

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Peter Hinrichsen, "Correcting the Correction", TPT, Vol. 32, # 7, Oct. 1994, p. 388.

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John E. Gribbin, "Not-So-Free Fall", TPT, Vol. 10, # 3, March 1972, p. 122.

V. V. Raman, "The Learning Tower of Piza Experiment", TPT, Vol. 10, # 4, April 1972, p. 196.

C. A. Randall, "OOPS...!", TPT, Vol. 10, # 6, Sept. 1972, p. 300.

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Robert P. Lanni, "The Method of Differences - Use and Misuse", TPT, Vol. 6, # 1, Jan. 1968, p. 35.

Richard O. Thomas, "A Device for Demonstrating Half-Thickness of Shielding Materials", TPT, Vol. 4, # 2, Feb. 1966, p. 77.

G. Guercio, "Determination of Gravitational Acceleration Using A Rubber Ball, AJP, Vol. 55, # 1, Jan. 1987, p. 59.

Carl G. Adler and Byron L. Coulter, "Galileo and the Tower of Pisa Experiment", AJP, Vol. 46, # 3, Mar. 1978, p. 199.

Mario Iona, "Why is g Larger at the Poles?", AJP, Vol. 46, (8), Aug. 1978, p. 790.

Mb-18, Freier and Anderson, A Demonstration Handbook for Physics.

Robert L. Wild, "Measurement of Acceleration of Gravity", Low-Cost Physics Demonstrations, (# 16), p. 12.

397, Was Galileo Right?" Christopher P. Jargodzki and Franklin Potter, Mad About Physics, p. 154, 297.

Robert P. Crease, "Dropping The Ball: The Legend of the Leaning Tower", The Prism & The Pendulum, Ch. 2, p. 21 - 35.

"Uniformly Accelerated Linear Motion", Selective Experiments in Physics, CENCO, 1940.

Mail Questions and Comments to: Dale Stille