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Chapter 9, Section 1 Describing and Measuring Motion. Thursday, February 11, 2010 Pages 282 -- 293. Objectives. Explain when an object is in motion and how motion is relative to a reference point. Calculate an object’s speed and velocity using SI units of distance.
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Chapter 9, Section 1 Describing and Measuring Motion Thursday, February 11, 2010 Pages 282 -- 293
Objectives • Explain when an object is in motion and how motion is relative to a reference point. • Calculate an object’s speed and velocity using SI units of distance. • Graph motion showing changes in distance as a function of time.
Vocabulary Words • Motion • Reference point • Meter • Speed • Velocity • Slope
How Do We Know Something Has Moved? • An object is in motion when its distance from another object is changing. • An object is moving or not depends on your point of view.
Reference Point • A place or object used for comparison to determine if something is in motion. • An object is in motion if it changes position relative to a reference point.
Describing Distance • The SI system is used to measure distance. • Distance is measured in meter. • Meter is a little longer than a yard.
Calculating Speed • If you know the distance an object travels in a certain amount of time, you know the speed of the object. • Speed=Distance/Time
Constant Speed If the speed of an object does not change. The speed is the same at all times during its motion. Example: Merry-go-round. Average Speed Objects do not ove at constant speeds for a long period of time. The total distance is divided by the total time to find the average speed. Constant Speed vs. Average Speed
Velocity • Speed in a given direction is called velocity. • Velocity can be calculated if you know both the speed and the direction of an object’s motion.
Graphing Motion • Time is shown on the x-axis (horizontal). • Distance is shown on the y-axis (vertical)
Slope • The steepness, or slant of a line on a graph is called its slope. • It tells you how fast one variable changes in relation to the other variable (rate of change). • The steeper the slope, the faster the motion.
Calculating Slope • Slope = Rise/Run • The RISE is the vertical difference between the two points. • The RUN is the horizontal difference between the two points.
Practice Graphing • Begin the Practice Worksheet in class and finish for homework. Due next meeting (2/12). • You can also practice online: • http://www.mathwarehouse.com/algebra/linear_equation/slope-of-a-line.php • http://www.algebrahelp.com/worksheets/view/graphing/slope.quiz
Homework • Graphing worksheet (2/12) • Workbook 9.1 (2/12) • Vocabulary quiz 9.1 (2/12)