1C20.15 - Free-Fall - Dropping Balls

Code Number:
1C20.15
Demo Title:
Free-Fall - Dropping Balls
Condition:
Good
Principle:
Free Fall, Terminal Velocity
Area of Study:
Mechanics
Equipment:
Pizza Pan, Set of Balls with the Same Diameter but Different Densities, Golf Ball, and Ping Pong Ball.
Procedure:

Choose any two different mass balls from the set and drop them from the same height onto the pizza pan.  You should be able to hear that they hit the pan at the same time as expected.  Repeat the experiment with the golf ball and Ping Pong ball and you should hear that they hit at different times.  This shows that the air has a much greater effect on the Ping Pong ball due to its larger diameter and small mass.  In effect it reaches a terminal velocity very quickly which is not seen with the golf ball over the short drop distances used.

References:
  • G. Bozzo, "'Free-Fall Demonstrations' in the High School Laboratory", TPT, Vol. 58, #1, Jan. 2020, p. 23.
  • 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.
  • Rod Cross and Crawford Lindsey, "Measuring the Drag Force on a Falling Ball", TPT, Vol. 52, #3, Mar. 2014, p. 169.
  • J. Messer and J. Pantaleone, "The Effective Mass of a Ball in the Air", TPT, Vol. 48, #1, Jan. 2010, p. 52.
  • Robert Ehrlich and Mary Lynn Hutchinson, "Random and Systemic Errors in Timing the Fall of a Coin", TPT, Vol. 32, #1, Jan. 1994, p. 51.
  • Byron L. Coulter and Carl G. Adler, "Can a Body Pass a Body Falling Through the Air?", AJP, Vol. 47, #10, Oct. 1979, p. 841.
  • Robert Ehrlich, "2.8. Timing the Fall of Dropped Objects", Why Toast Lands Jelly-Side Down, p. 32.
  • Robert Ehrlich, "A.1. Dropping Balls of Different Sizes", Turning the World Inside Out and 174 Other Simple Physics Demonstrations, p. 3 - 4.
  • John Henry Pepper and Henry George Hine, "Gravitaion", The Boy's Playbook of Science, p. 14.
  • Borislaw Bilash II and David Maiullo, "Heavier - Not Faster", A Demo a Day: A Year of Physics Demonstrations, p. 33.

Disclaimer: These demonstrations are provided only for illustrative use by persons affiliated with The University of Iowa and only under the direction of a trained instructor or physicist.  The University of Iowa is not responsible for demonstrations performed by those using their own equipment or who choose to use this reference material for their own purpose.  The demonstrations included here are within the public domain and can be found in materials contained in libraries, bookstores, and through electronic sources.  Performing all or any portion of any of these demonstrations, with or without revisions not depicted here entails inherent risks.  These risks include, without limitation, bodily injury (and possibly death), including risks to health that may be temporary or permanent and that may exacerbate a pre-existing medical condition; and property loss or damage.  Anyone performing any part of these demonstrations, even with revisions, knowingly and voluntarily assumes all risks associated with them.