Parabolic trajectory of projectiles
In the first half of the eighteenth century, the Dutch physicist Willem Jacob 's Gravesande invented a device to demonstrate experimentally that a body launched in a horizontal direction describes a parabolic trajectory.
A wooden base carries a support with a quarter-circle track and a vertical panel holding four equidistant rings along a parabolic line.
The marble ball is subject to a constant acceleration as it falls down the track. When the ball no longer has the track to support it, its "horizontal" projection motion is combined with the natural motion of uniformly accelerated fall. In consequence, the marble follows a parabolic path, as demonstrated by the fact that it moves through all the rings.
The experiment confirms the Galilean discovery of the parabolic trajectory as a compound motion, defined by the Pisan scientist in about 1609 and formalized in the Fourth Day of the Discourses and mathematical demonstrations concerning two new sciences.
Last update 04/feb/2008