Instant, Time Interval, Distance, Average Speed and Velocity | Phys 213, Study notes of Physics

Download Instant, Time Interval, Distance, Average Speed and Velocity | Phys 213 and more Study notes Physics in PDF only on Docsity! In this chapter we defined the terms needed to describe quantitatively the motion of point objects (or objects that can be treated as point objects) in one dimension (see also Table 2-1). Definitions In one dimension SUMMARY Instant t ≡ a single clock reading (a single point on a time line or axis) Time interval ∆t ≡ t2 − t1 (distance between two points on a time line or axis) Position (x or y) is a coordinate along an arbitrarily placed real number line with successive integers (in SI) 1 m apart. Displacement (2-1) Distance for path segments where there is no reversal of travel direction. Distances are always positive. (2-2) Average* velocity (2-3) Average* speed (2-4) Instantaneous velocity (2-5) Average* acceleration (2-7) Instantaneous acceleration Page 1 of 3Summary 8/22/2006http://edugen.wiley.com/edugen/courses/crs1354/pc/c02/content/touger8730c02_2_8.xform?c... Table 2-1 in Section 2-2 summarizes the relationships among these quantities and the type of question each quantity addresses. Graphs of x, v, and a versus t can provide meaningful descriptions of an object's motion. Slopes and vertical intercepts of these graphs have particular meaning. Because the slope always gives a rate of change and the vertical intercept always give an initial value, it follows that For straight lines (uniform slope), the average and instantaneous values are the same. Sections 2-3 and 2-4 provide further guidelines for interpreting graphs of x versus t and v versus t. The tables in those sections summarize key points. From the definition of average velocity, it follows that which for constant velocity situations becomes Whenever the acceleration is constant, From the definitions, we can use algebraic reasoning to obtain equations of motion that describe the motion of an object under particular conditions. When the condition is constant acceleration, Equations of motion (kinematic equations) for constant (uniform) a only: Things to remember when solving problems: (*averaged over ∆t) (2-8) For a graph of … The slope of a (secant/tangent) gives … And the vertical intercept gives … x versus t (Avg./instantaneous) velocity Initial position v versus t (Avg./instantaneous) acceleration Initial velocity (2-6) (2-6u) (2-10) (2-9) (2-11) (2-12) Make sure you get the picture—sketch the situation. Know how the relevant quantities are defined and be able to use the definitions. Think first about what is happening—what physical concepts or principles apply to the situation—and let that guide your Page 2 of 3Summary 8/22/2006http://edugen.wiley.com/edugen/courses/crs1354/pc/c02/content/touger8730c02_2_8.xform?c...