1.B.: Trajectories
Whether or not you have previously studied physics, from everyday experience you are familiar with the quantities used to describe the motion of particles, their position and velocity (or speed). The x, y and z coordinates of a particle as a function of time are known as the trajectory or orbit of a particle. The laws of classical physics predict the trajectory of a particle for all times once the position and velocity are known at some initial time. For example, if the position and velocity of a cannonball are known at the instant it leaves a cannon, the classical mechanics can predict the path taken by the cannonball at later times and where it will land.