Table of Mechanics Demonstration

List of Mechanics Equipment & Supplies

Lecture Demonstrations

Spring-Apart Air Track Gliders, 1N20.20

Topic and Concept:

Location:

AirTrackSpringString05-400.jpg

Abstract:

Using a scissors, cut a string holding a compressed spring between two air gliders initially at rest.

Equipment

Location

ID Number

2.25 m Air Track

Floor Item: ME, South Wall

Small & Large Gliders

ME, Bay A4, Shelf #4

Springs, Strings, & Scissors

ME, Bay A4, Shelf #3

Air Hose

Floor Item: ME, South Wall

Red & White Gas Carts

ME, Bay B1, Shelf #2

Important Setup Notes:

Setup and Procedure:

  1. Place air track on lecture bench, and connect the compressed air supply from the lower white panel of the Red & White Gas Cart to the track using an air hose.

  2. Place two gliders on the track, approximately centered.
  3. Turn on the air supply by opening the valve located on the lower white panel of the cart.
  4. If the gliders seem to slide in one direction, this is most likely due to the track being unlevel. Adjust the set screws until this no longer occurs. It is a good idea to do this ahead of time.
  5. Using a small section of string, make a tied loop, and hang it of a hanger on each glider so that the two gliders are connected.
  6. Carefully compress the spring into a U shape, and place it between the two gliders.
  7. When ready, cut the string with the scissors to release the potential energy.

Cautions, Warnings, or Safety Concerns:

Discussion:

A basic principle of physics is the conservation of momentum, namely linear momentum in this case. Stated mathematically, Pinitial = Pfinal. In this demonstration, Pinitial = 0. Thus, the sum of the individual momenta of our gliders must be zero after the spring is released. Mathematically, Pglider 1 = -Pglider 2 <=> mglider 1 * vglider 1 = -mglider 2 * vglider 2. If using gliders of equal mass, the two gliders will have the same speed and travel in opposite directions. If using two gliders of unequal mass, the more massive glider will move slower than the less massive one.

This demonstration can be performed with both the inelastic and elastic gliders (see photos for string placement).

AirTrackSpringString01-250.jpg

AirTrackSpringString02-250.jpg

AirTrackSpringString03-250.jpg

AirTrackSpringString04-250.jpg

AirTrackSpringString06-250.jpg

AirTrackSpringString07-250.jpg

AirTrackWithGliders-250.jpg

AirHose03-250.jpg

AirHose02-250.jpg

AirHose01-250.jpg

InelasticGliders-02-250.jpg

ElasticGliders-02-250.jpg

SpringsStrings01-250.jpg

SpringsStrings02-250.jpg

SpringsStrings04-250.jpg

SpringsStrings03-250.jpg

Videos:

References:

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