Chapter 2 Notes.

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Chapter 2 Notes

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

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

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

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?

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

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

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

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

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

An example

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

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