Coin and Feather Apparatus - Guinea Feather Tubes

(Amy Murphy)

Description: 

The Coin and Feather Apparatus - Guinea Feather Tube was invented by Isaac Newton.  It is a tall plastic cylinder which is capped at both ends.  One end of the tube also has a fitting for air evacuation.  A small vacuum pump is also needed.  Inside the tube there is a coin (penny) and a small feather (guinea feather).  When the tube is inverted students will see that the penny falls at a faster rate than the feather because of air resistance.  When the tube is connected to the vacuum pump and all air is removed form the tube a vacuum is created.  Now when the tube is inverted the penny and the feather will fall at the same rate.

Photographs: 
         

Principles illustrated: 
The Coin and Feather Apparatus - Guinea Feather Tube demonstrate the acceleration of gravity (g = 9.8 m/s/s, downward).  When the tube is inverted after air is removed, the penny and feather will fall at the same rate because the feather does not meet any air resistance. Guinea Feather Tube demonstrates that the Earth's gravity will accelerate all objects equally, regardless of mass will fall at exactly the same rate.  However, if you drop a penny and a feather under normal (atmospheric) conditions, the penny will hit the ground first because air resistance slows the feather down.  

Video:  

Fancy Free Fall in a Vacuum





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