Table and all attachments cost $40. Apparatus includes rotator table, Rotator part with brass circles to show shape of rotating earth, other Rotator part demonstrating centrifugal force (like Watt governor), Doppler whistle, and Rotator crank wheel.

Apparatus to demonstrate the conservation of momentum by the collision of balls having very hard surfaces is common, and ivory was a common material for the balls in the nineteenth century and early twentieth century. The use of ivory is not permitted now, and steel is the most common material for the balls. The balls on this apparatus are ivory.

Atwood's machine is a device to observe the acceleration of a moving system acted upon by small forces. Two unequal masses are hung over a pulley by a light cord. The pulley turns with low friction, and the acceleration of the system of masses can be measured. The mass accelerated is the sum of the two masses on the string, and the force producing acceleration is the difference in the weights of those two masses. In this device, the pulley carrying the cord turns on roller bearings, like those designed by Atwood in the 17th century. The second image shows the low-friction roller bearings

The rolling double cone serves as a demonstration of how gravity acts on an object’s center of mass. When released, the edges of the rolling double cone appear to move up its triangular support, but in reality the cone’s center of mass is still rolling downwards. The concept of the center of mass is older than the rolling double cone, which seems to have become a popular instrument in the 1700s. Some early versions of the cone were less elegantly constructed from rulers and screws, and could produce results that were unreliable. Nevertheless, its simplicity made it a useful and easy-to-understand demonstration when well carried out, and it was well-known in England by the eighteenth century. Several textbooks and course outlines from that time period cite it as one of the more important phenomena to be understood when it came to understanding laws of gravity and motion. The rolling double cone experiment was used in classrooms and illustrated and explained in textbooks to help explain to students how gravity worked. It is still being used in introductory physics classes at Grinnell today, as a way of demonstrating the importance of the concept of center of mass, and to show how counterintuitive it can be. -Lilly Haight 2018 References Clarke, Henry. The rationale of circulating numbers, with the investigations of all the rules and peculiar processes used in that part of decimal arithmetic. To which are added, several curious mathematical questions; With Some Useful Remarks on Adfected Equations, and the Doctrine of Fluxions. Adapted to the Use of Schools. London, 1777, pp. 89. Desaguliers, John T. A course of mechanical and experimental philosophy. Whereby any one, although unskill'd in mathematical sciences, may be able to understand all those phænomena of nature, which have been discovered by geometrical principles. London, 1725, pp. 3. Desaguliers, John T. A course of experimental philosophy. London, 1763. Worster, Benjamin. A Course of Experimental Philosophy. London, 1730.