1. Chapter 2 Notes

2. Scientific models Used to solve complex questions 3 types
Physical model-
Something you can physically manipulate
The car and ramp are examples
Conceptual model-
Descriptive models usually describing how something works
Copernicus describing how planets revolve around sun
Graphical model
Shows relationship between 2 variables

3. Graphical models
Can use graphs to predict values that you did not measure
Ex. Predicting speed in lab 2.1

4. Types of relationships
Strong positive relationship
Strong inverse relationship
Weak relationship
No relationship

5. Position vs. distance
Position: where something is compared to where it started including direction- as things move, position changes
Distance: interval of length without regard to direction- you could walk in a circle and your position would be the same, but you would have traveled a distance
Ex: You walk 7km north away from school, then walk back to the school- What is your position? What is your distance traveled?

6. Position vs. Time Graph The slope of this graph is speed at
any given time and position

7. Finding slope in general
Choose two points on a graph
Pt 1 (0.5, 30) Pt 2 (1.5, 60)
Use the following formula:
The units show you that the slope you found is speed

8. Average vs. Instantaneous speed
Average speed- speed that results from whole journey
Total distance/time
Instantaneous speed- speed at a particular point on the journey
Position/ time

9. Acceleration Rate of change in speed of an object
Formula: Change in speed/change in time
Units: cm/ sec2

10. Acceleration Occurs when Deceleration- decrease in speed over time
You speed up
You slow down
You change direction
Deceleration- decrease in speed over time
0 acceleration- traveling at a constant rate or stopped

11. An example

12. Free Fall Acceleration due to gravity: 9.8m/s2
This means that for every second an object falls, its speed increases by a factor of 9.8m/s
Ignore air resistance

13. Speed vs time graph Find slope- the units you get are cm/sec2
In other words, slope of a speed vs time graph is acceleration