2 step process to solve motion problems: motion diagram: develop a simplified representation of motion so that the key elements stand out, analyze the motion with the language of mathematics. Motion: the change of an object"s position or orientation with time. Trajectory: the path along which an object moves. 4 basic types of motion: straight-line motion (1 dimensional, projectile motion, circular motion, rotational motion. Section 1. 2: position and time, putting numbers on nature. Displacement: the difference between a final position (xf) and an initial position (xi or x0). A time interval ( t) measures the elapsed time as an object moves from an initial position (xi) at time ti , to a final position (xf) at time tf. Uniform motion (definition): motion at a constant speed. For an object in uniform motion, successive frames of the motion diagram are equally spaced. This means that the object"s displacement ( x) is the same between successive frames.