![]() The geometrical idealization of projectile trajectories allows to neglect physical effects, like air resistance. If one knows it’s distance in a given time, then one can describe the path of the body. 67): One of the properties of the parabola is that the parameter of its axis or of one of its diameters is the third proportional to the abscissa of this diameter and its ordinate. ![]() ![]() (Copyright © 2018 KB)Īnother example for Du Châtelet’s discussion of projectile trajectories is the following one (InstPhy, § 511 Fig. The parabola BED is called the path of the moveable body, and the right line ST which subtends this parabola BD described by this body in its motion, is called the amplitude of this path, and the angle CBT is called the angle of elevation. décrite par ce corps dans son mouvement, s’appelle l’amplitude de ce chemin, & l’angle CBT. s’appelle le chemin du mobile, & la ligne droite ST. 68, the “amplitude” and the “angle of elevation” are defined as follows: 66, Du Châtelet explains, for example, the throwing parabola from B to D when the projectile is thrown in a horizontal direction (the direction of the projectile force is parallel to the horizon). In all three cases, the line that the body describes when it is thrown in a direction vertical or oblique to the horizon is a parabola. (A force acting for a given amount of time will change an object’s momentum.) Du Châtelet then analyses the curve of a projectile in a non-resisting medium for cases of vertical, horizontal and oblique throws. What Du Châtelet really describes is, from today’s point of view, the change in momentum, or impulse. It is described as a specific kind of an impressed force that can be directed perpendicularly or in parallel to the horizon, or indeed it can make any angle with it (InstPhy, § 502). By contrast, Du Châtelet introduces the projectile force. In today’s teaching cources it is taught that the only force of significance that acts on the object is gravity. The study of such motions is called ballistics. Projectile motion is a form of motion experienced by a thrown object (a projectile) along a curved path. This chapter deals with a special case of the motion of bodies, namely with projectile motion.
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