1. DESCRIBING POSITION
How would you describe where you are right now?
Each description states your location relative to a certain point.

2. DESCRIBING POSITION
A Reference point is the starting point you choose to describe the location, or position of an object.
A Position is an object’s distance and direction from a reference point. A complete description of your position includes a distance, a direction and a reference point.

3. DESCRIBING MOTION Describing Position in Two Dimensions
Sometimes you need to describe an object’s position using more than one reference direction. When you describe a position using two directions, you are using two dimensions.

4. DESCRIBING MOTION Describing Position in Two Dimensions
Examples of reference directions: north, south, east, west, right, left, up, down.

5. DESCRIBING MOTION Locating a Position in Two Dimensions
Finding a position in two dimensions is similar to finding a position in one dimension. First, choose a reference point. Next, specify directions (north and east).

6. DESCRIBING MOTION Locating a Position in Two Dimensions
Then, determine the distance along each reference direction.
Dimension.- Distance or length measured in one direction.

7. DESCRIBING MOTION Describing Changes in Position
Sometimes you need to describe how an object’s position changes.
Motion.- From latin motere, means «to move». Is the process of changing position.

8. DESCRIBING MOTION Motion Relative to a Reference Point.
An object is in motion if its position changes relative to a reference point.
Based on Fig. 4 from page 13 the man in the boat is not in motion compare to his finding pole.

9. DESCRIBING MOTION Motion Relative to a Reference Point.
He is in motion compared to the buoy because the man’s distance from the buoy changes.

10. DESCRIBING MOTION Motion Relative to a Reference Point.
Quantities Scalar Quantity Vector Quantity
Contains magnitud and unit
e.g. 10 m
Contains magnitud, unit and direction
e.g. 10 m north

11. DESCRIBING MOTION Distance and Displacement
Distance describes how far an object has moved, distance depends on the path taken, and it is a scalar quantity.

12. DESCRIBING MOTION Distance and Displacement
Displacement is the difference between the initial position and final position of an object. Displacement is a vector quantity because it has direction

13. DESCRIBING MOTION Distance and Displacement
The distance is the red path.
The displacement is the blue arrow.

14. DESCRIBING MOTION Distance and Displacement
1 Km
HOUSE
Starting Point
0.5 Km
SCHOOL
Ending Point
1 Km
The car’s displacement was 0.5 Km to the south
The distance traveled was 2.5 km

15. DESCRIBING MOTION Distance and Displacement
Examples:
Sandra runs 2.5 Km every day
The next mall is only 1 Km away
My house is 10 miles away
Susan walks 200 m to the south
Alberto is 10,000 miles north from his house
10 km north, 5 km west

16. DESCRIBING MOTION Distance and Displacement
Students will analyze the figure 5 from page 13.
HW Based on figure 5.
What is the distance and the displacement when a player runs to third base?

17. SPEED AND VELOCITY Speed and Velocity
Imagine that you are traveling in a car at 80 Km/h. Can we say that is speed or velocity?

18. SPEED AND VELOCITY Speed
Speed is a measure of the distance an object travels per unit of time. It is a scalar quantity.
Speed = Distance v= d
Time t
v=speed= m/s, Km/h, mph
d=distance=m, Km, mile
t= time=min, hr, s

19. SPEED AND VELOCITY Speed
Constant Speed is is the rate of change of position in which the same distance is traveled, see Fig. 6
Instantaneous speed is speed at a specific instant in time.

20. SPEED AND VELOCITY Speed
Average speed is the total distance traveled divided by the total time taken to travel that distance.

21. SPEED AND VELOCITY Speed
Example
Ball 3m 8m
16m
Lift
1 sec A
2 s B
3 s C
The instantaneus speed for A is 3 m/s
The instantaneous speed for B is 8m= 4m/s 2s
The average speed is equal to 16m = 5.3 m/s 3

22. SPEED AND VELOCITY Velocity
Velocity includes the speed of an object and the direction of its motion. It is a vector quantity.
Example: 2 car with the same speed (50Km/h) have different velocities if the are traveling at different directions
50 km/h

23. SPEED AND VELOCITY Average Speed
Example: Melissa shot a model rocket 360m into the air. It took the rocket 4 s to fly that far. What is the average speed of the rocket?
Distance: d=360m
Time: t=4s
v=d/t =360m/4s
v= 90m/s
Answer: The average speed was 90 m/s

24. SPEED AND VELOCITY Homework
It takes Ahmed 50 s on his bicycle to reach his friend’s house 250 m away. What is his average speed?
A Truck makes a trip that covers 2,380 Km in 28 hours. What is the driver’s average speed?
v= d t

25. REVIEW Scientific Notation
The number has to be between 1 and 10
If the exponent is negative, the number is small (< 1)
If the exponent is positive, the number is big (>1)
The exponent is the number of places you moved the decimal point, NOT the number of zeros.
Example: 2.8x107 = 28,000,000
2.8x10-7=

26. REVIEW Percent Error
It is the expression of error as a percentage of accepted value.
Formula:
experimental value – accepted value x 100%
accepted value
Experimental value=97.5 C
Accepted value= 100 C
( ) x100% = 2.5%
100

27. REVIEW Experimental Groups
The experimental group is used to study how a change in the independent variable changes the dependent variable.
Example: You might set up an experiment to determine which of the 3 fertilizers helps plants to grow up the biggest.

28. REVIEW Experimental Groups
Independent
Variable
Dependent
Variable
Constants
Plants
Type of plant
Soil
Amount of water
Fertilizers
Growth 1
Oak
Clay
50 gallons A
2.0 cm 2 B
2.5 cm 3 C
3.0 cm 4
None
1.5 cm
Experi-mental
Group
Control Group