PURPOSE: To demonstrate that bodies that fall with unequal accelerations in air fall with the same acceleration in the absence of air.

DESCRIPTION: The ball falls faster than the feather with air in the tubes. When the air is pumped out, the ball and the feather fall with the same acceleration. The double tube assembly is rotated rapidly on its axis to initiate the free fall.

The center photograph shows the ball (left tube) and the feather (right tube) falling in partial vacuum; in the photograph at the right the tubes contain air at atmospheric pressure.

SUGGESTIONS:

REFERENCES: (PIRA 1C20.10)

The original film footage of the astronauts dropping a hammer and a feather on the moon, along with a number of other demonstrations performed at the same time, will be found at the URL http://history.nasa.gov/alsj/a15/a15.clsout3.html. Go to the time labelled 167:22:06 and select either the 0.8Mb ".mov" format (difficult to see) or the 6.2Mb ".mpg" format (easier to see).

EQUIPMENT: Vacuum pump with double tube assembly, as photographed.

SETUP TIME: None.