 # Chapter 9, Section 1 Describing and Measuring Motion Thursday, February 11, 2010 Pages 282 -- 293 Thursday, February 11, 2010 Pages 282 -- 293.

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Chapter 9, Section 1 Describing and Measuring Motion Thursday, February 11, 2010 Pages 282 -- 293 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.  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  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  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 vs. Average Speed  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.  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.

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.  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)  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.  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.  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  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)  Graphing worksheet (2/12)  Workbook 9.1 (2/12)  Vocabulary quiz 9.1 (2/12)

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