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Packard's apparatus is used to investigate
the spatial relationships of a body in vertical motion in a constant gravitational
field. It was invented by John C. Packard of Brookline High School in Brookline, Massachusetts, and was patented on December 17, 1907. The original manufacturer was the L.E. Knott Apparatus Company of Boston, which sold it for $6.25 in 1916. The inclined plane is leveled from side to side using the spirit level at the top. A piece of graph paper is placed on the sheet of plate glass forming the top of the apparatus, and over this is laid a sheet of carbon paper, face down. |
A [missing] horizontal ramp is used to project
a steel ball sideways, and the heavy ball (about an inch in diameter) follows
a parabolic path down the paper. This example, at Kenyon College, still has
the mark of the ball on the graph paper dating from its last use, probably
in the nineteen thirties or forties..
The horizontal motion of the ball provides the time axis, and the vertical motion gives a record of the body's motion. Since the body moves in a constant gravitational field, the position vs. time graph is a parabola.
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Home Page | Return to Home Page The horizontal motion of the ball provides the time axis, and the vertical motion gives a record of the body's motion. Since the body moves in a constant gravitational field, the position vs. time graph is a parabola.