Table of Mechanics Demonstration List of Mechanics Equipment & Supplies Lecture Demonstrations

# Tablecloth Pull, 1F20.30

Topic and Concept:

Location:

Abstract:

AKA Beaker and Cloth. A beaker partially filled with water is placed on a seamless tablecloth favoring an edge. The tablecloth is quickly yanked out from under the beaker, leaving the beaker in place without spilling any water. Thus, illustrating Newton's first law.

 Equipment Location ID Number Tablecloth ME, Bay A7, Shelf #5 Two-Liter Beaker ME, Bay A7, Shelf #5

Important Setup Notes:

• This demo will require practice.

Setup and Procedure:

1. Place the tablecloth on a table.
2. Partially fill a beaker with water. Add food coloring to water for contrast.
3. Place beaker on and near an edge of the tablecloth.

Cautions, Warnings, or Safety Concerns:

• Make sure to perform this demo with adequate distance from the audience to prevent exposure to flying glass in the event of a failed demo.
• Make sure the cloth being used is free of seams or other defects that could trip the beaker.

Discussion:

The quick jerking motion of the tablecloth has enough energy to overcome the normal force of the beaker and the frictional forces between the cloth, table, and beaker. First pull the tablecloth with the water filled beaker on it slowly, thus showing that the beaker moves with the cloth. Just before everyone thinks your going to make a mess. Give the cloth that quick jerk. The beaker will remain at rest and not move much. The water may slosh back and fourth a little.

Videos:

References:

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