1. Warm-Up: September 15, 2015 Using the graph and line of best fit from yesterday’s class, estimate the length of the spring when 50 g is hung from it.

2. Page 14 Answers

3. Homework Questions?

4. Representing Motion Chapter 2

5. Essential Questions How can we represent motion? What are position, distance, displacement, and time interval, and how are they related?

6. Motion Diagrams A motion diagram is a series of images showing the positions of an object at different times.

7. Particle Model Particle Model: A motion diagram where the object in motion is replaced by a single point at its center – Requires that the object’s size be much less than the distance traveled The time interval is the elapsed time between points. – Must be constant.

8. Textbook – Page 33 Example of a motion diagram and its corresponding particle model.

9. Where and When? – Section 2.2 Coordinate System: Tells location of zero and direction in which the variables increase Origin: The point where all variables equal 0 Use an arrow starting from the origin and pointing to the object’s current position to show its distance from the origin.

10. Vectors and Scalars

11. Adding Vectors Draw an arrow for each vector Place them tip to tail The sum, or resultant, points from the tail of the first vector to the tip of the last vector

12. Δ: Greek letter Delta

13. Subtracting Vectors

14. Think-Pair-Share: Page 42 #21-23 21) Use the position-time graph of the hockey puck to determine when it was 10.0 m beyond the origin. 23)Use the position-time graph for the hockey puck to determine how much time it took for the puck to go from 40 m beyond the origin to 80 m beyond the origin. 22)Use the position-time graph of the hockey puck to determine how far it moved between 0.0 s and 5.0 s.

15. Think-Pair-Share: Page 42 #24 Look at the particle model and position-time graph shown. Do they show the same motion? How do you know?

16. Think-Pair-Share: Page 42 #24 You now know the time interval in the particle model is 2.0 s. Do they show the same motion? How do you know?

17. Average Velocity The slope of a linear position-time graph Take final and initial points of any position- time graph and use the formula Average speed is the magnitude of average velocity

19. Warm-Up: September 16/17, 2015 Draw a distance-time graph and a particle model diagram that show the motion of an object at a constant speed of 25 cm/s

20. Continuing Chapter 2

21. Example 1 Stanley is riding his bicycle along a straight road, headed north. The graph below shows how far away from the edge of his driveway he is at different times. Calculate his a)Average speed b)Average velocity

22. Equation of Motion

23. Breakdown Format 1.What information does the problem give me? 2.What is the question asking for? 3.What formula(s) do I need? 4.Check for unit consistency 5.Replace variables in the formula with the numbers in the problem. 6.Calculate the correct answer. 7.Is the answer reasonable?

24. Example 2 A car enters I-5 at a point 10 miles north of the US-Mexico border and drives north at a constant velocity of 60 mph. Where is the car after 30 minutes?

25. You-Try #2 A sprinter is running a 100.-meter dash. He runs the first 20. meters in 2.7 seconds. He runs the remainder of the race at an average speed of 10. m/s. How long does it take the runner to finish the race? – Calculate the time for final 80. meters – Calculate the time for the whole 100.-meter dash

26. Instantaneous Velocity Instantaneous Velocity (v or ): The speed and direction of an object at a particular instant For objects that change velocity, we will typically use instantaneous velocity in our calculations

27. Think-Pair-Share: Page 47 #29-31 Sort the four lines from largest to smallest (most positive to most negative) 30) Velocity 29) Speed 31) Initial position

28. Non-Constant Velocity

29. Assignments Read Chapter 2 Page 53 #34, 47, 49-54, 59, 60 You have 30 minutes to work on this. Scientific calculator check-out from library