Study of motion _________________________________________________________________________________________________
19. Free fall
Free fall is a special type of motion in which the only force acting upon an object is gravity.
Objects that are said to be undergoing free fall, are not encountering a significant force of air resistance; they are falling under the sole influence of gravity.
Under such conditions, all objects will fall with the same rate of acceleration, regardless of their mass.
Watch the video about the Apollo 15 Hammer-Feather drop on the Moon.
At the end of the last Apollo 15 moon walk, Commander David Scott performed a live demonstration for the television cameras.
He held out a geologic hammer and a feather and dropped them at the same time. Because they were essentially in a vacuum (no air resistance), there was no air resistance and the feather fell at the same rate as the hammer, as Galileo had concluded hundreds of years before - all objects released together fall at the same rate regardless of mass.