Physics Demonstrations
Department of Physics and Astronomy
Physics Demonstrations

Coin and Feather Falling Simultaneously in Air and in a Vacuum

Identifier: M: D - 010

A coin and a feather rest inside a sealed plastic tube.

Concept Overview

In the absence of air resistance, all objects will fall at the same rate.

Lecturer Procedure

Step(s) to FollowExpected Result
  1. Open the stopcock on the cylinder.
  2. Hold tube vertically.
  3. Suddenly, reverse upper and lower ends of tube.

The coin will reach the bottom of the tube NOTICEABLY quicker than the piece of cotton.

(hear coin clink, see cotton trail)

  1. Attach hose from vacuum pump to tube.
  2. Turn on vacuum pump
  3. Pump until sound indicates a reasonably good vacuum.
  4. Turn cock to closed position.
  5. Repeat steps 2&3 above
Coin will be heard to clink; cotton will appear to fall just as fast as the coin.

Historical References; Taken from original work of Percy H. Carr, 1970 

“This is the classical experiment of the guinea and the feather. The cotton tuft is superior to a feather because it is readily seen by the students at a distance. It is also more durable than the feather.”


“Care to discuss the parachute problem on Mars? Or the Moon? Or Venus?"

Video Demonstration

Tutorial: Set-up Instructions for M: D - 10
Transcript:

There are no spoken words with this recording.

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