Apparatus for comparison of acting forces on free falling bodies

The Machine, whereby the Forces of Bodies, falling directly, are compar'd is an experiment in which brass balls are dropped from different heights into a box filled with clay. The balls leave imprints of different depths in the clay and the forces acting can be compared with each other on the basis of the imprints.  The variables used are on the one hand the different drop heights and on the other hand brass balls with different masses.

The experiment was designed by Willem Jakob s'Gravesande. He described the structure of the device and the experiment carried out with it for the first time in 1747 in his Mathematical Elements of Natural Philosophy, confirm'd by Experiments. In doing so, he also gives more or less exact dimensions of the device, which enables a detailed replica. s'Gravesande's hypothesis was that at different drop heights with different weights, imprints are created in the clay that differ from each other. According to him, if two imprints in the clay resemble each other, the same forces have been at work.

 For the reproduction of and experimentation with the device, our BA candidate Svea Behmer was primarily guided by a copper engraving by s'Gravesande (1747) and the accompanying descriptions. The aim of their work was to reconstruct the drop tests, which s'Gravesande probably carried out himself. These efforts were widely successful once Svea Behmer had established enough knowledge to generate the composition of the clay at the bottom of the machine.

's Gravesande, Willem Jacob (MDCCXXXVII. [1737): Mathematical elements of natural philosophy. Confirm'd by experiments: or, an introduction to Sir Isaac Newton's philosophy. Translated into English by J. T. Desaguliers, The fifth edition. London: printed for J. Senex in Fleet-Street W. Innys and R. Manby in St. Paul's Church-Yard and T. Longman in Pater-Noster-Row.

's Gravesande, W. J. (1722): Essai d'une nouvelle théorie du choc des corps fondée sur l'éxpérience: T. Johnson (Journal literaire de la Haye).