Two large blocks of equal size, connecting spring, Plywood shelf
tennis balls on a string in a bucket

 

Code Number: 1G20.40

Demo Title: Springs & Weights or Bucket & Elastic

Condition: Good

Principle: Absence of Friction in Freefall

Area of Study: Mechanics

Equipment:

Two large blocks of equal size, connecting spring, Plywood shelf, Styrofoam block.

Procedure:

Connect the two blocks with the spring and spread them apart to the ends of the shelf.  This leaves the spring under tension but the blocks do not move together because of the friction.  Lift the shelf and everything on it and drop it onto the foam pad.  As it drops, the spring will pull the blocks together as there is no friction during freefall.

Stretch the elastic string so that the tennis balls hangs over the edge of the bucket.  Hold the bucket up high, drop it, and then catch it about waist high.  You will observe that immediately after you release the bucket and it achieves freefall, the tennis balls will be pulled back into the bucket by the elastic.

References:

  • Morton Tavel, "Reference Frames", TPT, Vol. 41, #4, Apr. 2003, p. 197.
  • Jeffrey C. LaCombe and Matthew B. Koss, "The Make-It-Yourself Drop-Tower Microgravity Demonstrator", TPT, Vol. 38, #3, Mar. 2000, p. 143.
  • John A. McClelland, "Simulating Microgravity", TPT, Vol. 38, #6, Sept. 2000, p. 328.
  • Howard Pearlmas, Dennis Stocker, Daniel Gotti, David Urban, Howard Ross, and Thomas Sours", TPT, Vol. 34, #3, Mar. 1996, p. 172.
  • S. K. Chakarvarti, "A Demonstration on Weightlessness", TPT, Vol. 16, #6, Sept. 1978, p. 391.
  • Noel J. Petit and Philip A. Johnson, "Uniform Acceleration Demonstration", AJP, Vol. 47, #3, March 1979, p. 287.
  • Ken Zetie, "Dieting Isn't The Only Way To Lose Weight", Physics Education, Vol. 39, #1, Jan. 2004, p. 37.
  • Julius Sumner Miller, Q52 & A52, Millergrams I – Some Enchanting Questions for Enquiring Minds, p. 37 & 95.