1. Many words are used when describing motion.
8.1 The Language of Motion
Many words are used when describing motion.
Many of these words have specific meanings in science.
Some common words used to describe motion include:
___________
Describe the motion of the soccer ball before and after it is kicked.
What key words did you use when describing this situation?
See pages
(c) McGraw Hill Ryerson 2007

2. Direction Makes a Difference
Quantities that are measured or counted have a _________but may also contain a ________.
Magnitude refers to the size of a measurement or the amount you are counting.
Quantities that describe magnitude but do not include direction are called ___________ quantities or scalars.
Example: 25 seconds
Quantities that describe magnitude and also include direction are called ______ quantities or ____________.
Example: 5 km north
Every time you use a map or give directions, you are using vectors.
See page 346
(c) McGraw Hill Ryerson 2007

3. The _____________ for both distance and position is metres, m.
____________ (d) is a scalar quantity that describes the length of a path between two points or locations.
Example: A person ran a distance of 400 m.
____________( ) is a vector quantity that describes a specific point relative to a reference point.
Example: The school is 3.0 km east of my house.
The _____________ for both distance and position is metres, m.
A car leaves home and drives 10 km to the store and then returns home. The car has driven a total distance of 20 km but its final displacement is 0 km.
See pages
(c) McGraw Hill Ryerson 2007

4. Time Interval and Position
_____ (t) is a concept that describes when an event occurs.
Initial time (ti) is when the event began.
Final time (tf) is when the event finished.
Time interval is the difference between the final and initial times.
_________________ is calculated by:
The time interval to move from the fire hydrant to the sign is calculated by:
The position of the sign is 7 m east of the tree.
See page 348
(c) McGraw Hill Ryerson 2007

5. Displacement and Distance
____________ describes the straight-line _______ and ________ from one point to another.
Displacement describes how much an object’s position has changed.
Displacement is equal to the final position minus the initial position.
The _______________ for displacement is metres, m.
Between 2 s and 5 s the skateboarder’s displacement is 5 m [E]. The skateboarder’s distance travelled is 5 m.
See page 349
(c) McGraw Hill Ryerson 2007

6. Watch for Signs
When using _________________ , opposite directions are given opposite signs.
Between 0 s and 15 s the person’s displacement is
Common sign conventions
= 10 m [W] – 5 m [E]
= -10 m – 5 m
= -15 m
= 15 m [W]
What distance did the person walk in this same time interval?
See page 349
(c) McGraw Hill Ryerson 2007

7. Uniform Motion
Objects in __________________ travel equal displacements in equal time intervals.
Objects in uniform motion do not speed up, slow down, or change direction.
The position of the ball in this photo is shown at equal time intervals. How would you determine if this motion is uniform motion?
See page 350
(c) McGraw Hill Ryerson 2007

8. Graphing Uniform Motion
Motion of an object can be analyzed by drawing a ____________________ graph.
A position-time graph plots ________ data on the vertical axis (y axis) and ____ data on the horizontal axis (x axis).
A ________ line is a smooth curve or straight line that most closely fits the general shape outlined by the points.
________ motion is represented by a straight line on a position-time graph.
The straight line passes through all the plotted points.
A straight line passing through the plotted data indicates uniform motion.
See page 351
(c) McGraw Hill Ryerson 2007

9. Slope
The slope of a graph refers to whether a line is horizontal or goes up or down at an angle.
______________ slope
Slants up to the right
Indicates motion in the direction of the positive y axis
___________ slope
Horizontal line
Indicates that the object is stationary
Slants down to the right
Indicates motion in the direction of the negative y axis
See pages
Take the Section 8.1 Quiz
(c) McGraw Hill Ryerson 2007

10. Velocity is a __________ quantity and must include direction.
8.2 Average Velocity
__________( ) is the distance an object travels during a given time interval divided by the time interval.
Speed is a scalar quantity.
The SI unit for speed is metres per second (m/s).
___________ ( ) is the displacement of an object during a time interval divided by the time interval.
Velocity describes how fast an object’s position is changing.
Velocity is a __________ quantity and must include direction.
The direction of the velocity is the same as the direction of the displacement.
The ______ for velocity is metres per second (m/s).
These two ski gondolas have the same speed but have different velocities since they are travelling in opposite directions.
See pages
(c) McGraw Hill Ryerson 2007

11. Calculating the Slope of the Position-Time Graph
The slope of a graph is represented by rise/run.
This slope represents the change in the y-axis divided by the change in the x-axis.
On a position-time graph the slope is the change in position ( ) divided by the change in time ( ).
The steeper the slope the greater the change in displacement during the same time interval.
Which jogger’s motion has a greater slope?
Which jogger is moving faster?
See pages
(c) McGraw Hill Ryerson 2007

12. The slope of a position-time graph is the object’s _______________ .
Average Velocity
The slope of a position-time graph is the object’s _______________ .
Average velocity is the rate of change in position for a time interval.
The symbol of average velocity is:
On a position-time graph, if forward is given a positive direction:
A positive slope means that the object’s average velocity is _______ .
A negative slope means that the object’s average velocity is _____________ .
Zero slope means the object’s average velocity is zero.
See pages
(c) McGraw Hill Ryerson 2007

13. Calculating Average Velocity
The relationship between average velocity, displacement, and time is given by:
Use the above equation to answer the following questions.
What is the average velocity of a dog that takes 4.0 s to run forward 14 m?
A boat travels 280 m east in a time of 120 s. What is the boat’s average velocity?
See page 368
(c) McGraw Hill Ryerson 2007

14. Calculating Displacement
The relationship between displacement, average velocity, and time is given by:
Use the above equation to answer the following questions.
What is the displacement of a bicycle that travels 8.0 m/s [N] for 15 s?
A person, originally at the starting line, runs west at 6.5 m/s. What is the runner’s displacement after 12 s?
See page 369
(c) McGraw Hill Ryerson 2007

15. Use the above equation to answer the following questions.
Calculating Time
The relationship between time, average velocity, and displacement is given by:
Use the above equation to answer the following questions.
How long would it take a cat walking north at 0.80 m/s to travel 12 m north?
A car is driving forward at 15 m/s. How long would it take this car to pass through an intersection that is 11 m long?
See page 369
(c) McGraw Hill Ryerson 2007

16. Converting between m/s and km/h
To convert from km/h to m/s:
Change km to m: 1 km = 1000 m
Change h to s: 1 h = 3600 s
Multiply by 1000 and divide by 3600 or
Divide the speed in km/h by 3.6 to obtain the speed in m/s.
For example, convert 75 km/h to m/s.
Speed zone limits are stated in kilometres per hour (km/h).
See page 369
(c) McGraw Hill Ryerson 2007

17. Converting between m/s and km/h
Try the following unit conversion problems.
Convert 95 km/h to m/s.
A truck’s displacement is 45 km north after driving for 1.3 h. What was the truck’s average velocity in km/h and m/s?
What is the displacement of an airplane flying 480 km/h [E] during a 5.0 min time interval?
See page 369
(c) McGraw Hill Ryerson 2007