43.8 x 24.8 x 58.3
Carved and inlaid wood,
steel and brass
INDEX 1788 : D.III.151
Planum inclinatum mobile cum subnexo quadrante antea indicato. Cylindrus plumbeus cum duabus rotis et axiculo ex orichalco, olioque apparatu.
Moveable inclined plane with attached quadrant, as previously indicated. Lead cylinder with two wheels and a small brass axle, and other apparatus.
This apparatus is intended for the study of the state of equilibrium on an inclined plane. The piece is made up of a wooden plank set horizontally on four feet. Joined to this plank by means of a hinge is a second plank used as an inclined plane. The measurement of the slope angle is by means of a graduated brass quadrant mounted on the base of the instrument alongside the inclined plane. The quadrant is at right angles to the inclined plane and its centre of curvature coincides with the end of the plane's rotational axis.
On the inclined plane there is a lead cylinder with a metal bracket clipped to its axle, maintained in position by a string tied to the bracket. This string passes over a brass pulley situated at one end of a wooden rod mounted on the base of the apparatus. From the other end of the cord an object is suspended, the weight of which is chosen according to the angle of inclination of the plane. The experiment carried out with this equipment consists in establishing a relation of equilibrium between the weight of the cylinder, the slope of the plane and the weight of the object suspended from the string.
The rod holding the pulley is attached to a cogwheel situated alongside another wheel fixed to the base. This second wheel is perforated near its rim so that a bolt can be inserted. When the bolt is between the teeth of the cogwheel, the rod stays fixed at the position and the angle selected by the experimenter.
From Colégio dos Nobres, catalogue n.º 143.
Desaguliers, Jean-Théophile, A Course of Experimental Philosophy, London, 1734, Vol. I, p. 108, Pl. 11, Fig. 2.