This model illustrates an experiment devised by Galileo to demonstrate that a body projected in a non-vertical direction always follows a parabolic trajectory.

The parabolic trajectory of a projectile results from the combination of a uniform horizontal motion and the natural motion of falling, which is constantly accelerated as time passes.

Galileo compared these combined motions to the forces that determine the curvature of a chain suspended from the ends (catenary): a horizontal force (pulling) and a vertical force (gravity).