1. Objectives 1.Define and calculate acceleration 2.describe how the physics definition of acceleration differs from the everyday definition of acceleration. 3.Interpret and analyze position vs. time and velocity vs. time graphs for motion. 4.Calculate acceleration in situations involving uniform motion. 5.Solve problems involving acceleration.

2. Warm Up When the 10 km/h bikes that are riding towards each other are 20 km apart, a bee begins flying from one wheel to the other at a steady speed of 30 km/h. When it gets to the wheel, it abruptly turns around and flies back to touch the first wheel, then turns around and keeps repeating the back-and-fourth trip until the bikes meet, and “squish”! 20 km 10 km/h 30 km/h How many km did the bee travel in its total back-and-forth trips?

3. D vs. T Graph distance p time Runner a Runner b Who is running faster at point “p”? Who covers the most distance in the race? Who started closer to the finish line in this race around the track?

4. Graphical Analysis: Distance versus time Give a qualitative description of the motion depicted. x (m) t (min) 0.51.01.52.02.53.03.5 1.0 2.0 1.0 2.0

5. Acceleration 1.What comes to mind when you think of acceleration? http://www.youtube.com/watch?v=0e3B9WFahVk 2. Do you think the Physics definition of acceleration is different?

6. 2-4 Acceleration Acceleration is the rate of change of velocity.

7. Motion of Car Why is this graph a truer representation of a the motion of the car?

8. Velocity Give a qualitative description of the two motions depicted. V (m/s) t (s)

9. Graphical analysis: Velocity versus time a. b.

10. Acceleration Acceleration is defined as the rate at which an object changes its velocity. Vector Quantity. An object is accelerating if it is changing its velocity.

11. Average Acceleration Units for Acceleration m/s 2 m/min 2 m/h 2 Km/s 2

12. Problem A car accelerates from 12 m/s to 25 m/s in 6.0 s. What was its acceleration?

13. About Accelerations... An object with a zero acceleration always move at the same speed. An object with a positive acceleration will go faster and faster towards the right. An object with a negative acceleration will go faster and faster towards the left. If an object has an acceleration, the little arrows WILL NEVER be evenly spaced. If an object has an acceleration of zero, the little arrows WILL ALWAYS be evenly spaced.

14. 2-4 Acceleration Acceleration is a vector, although in one- dimensional motion we only need the sign. The previous image shows positive acceleration; here is negative acceleration:

15. 2-4 Acceleration There is a difference between negative acceleration and deceleration: Negative acceleration is acceleration in the negative direction as defined by the coordinate system. Deceleration occurs when the acceleration is opposite in direction to the velocity.

16. 2-4 Acceleration The instantaneous acceleration is the average acceleration, in the limit as the time interval becomes infinitesimally short. (2-5)

17. The average velocity of an object during a time interval t is The acceleration, assumed constant, is 2-5 Motion at Constant Acceleration

18. Page 39 # 17 A sprinter accelerates from rest to 10.0m/s in 1.35s. What is her acceleration (a) in m/s 2 and (b) in km/h 2 ?

19. 2-5 Motion at Constant Acceleration In addition, as the velocity is increasing at a constant rate, we know that Combining these last three equations, we find: (2-8) (2-9)

20. 2-5 Motion at Constant Acceleration We can also combine these equations so as to eliminate t: We now have all the equations we need to solve constant-acceleration problems. (2-10) (2-11a) (2-11b) (2-11c) (2-11d)

21. Show how to derive those equations on page 27. Give out formula sheet.

22. 2-6 Solving Problems 1. Read the whole problem and make sure you understand it. Then read it again. 2. Decide on the objects under study and what the time interval is. 3. Draw a diagram and choose coordinate axes. 4. Write down the known (given) quantities, and then the unknown ones that you need to find. 5. What physics applies here? Plan an approach to a solution.

23. 2-6 Solving Problems 6. Which equations relate the known and unknown quantities? Are they valid in this situation? Solve algebraically for the unknown quantities, and check that your result is sensible (correct dimensions). 7. Calculate the solution and round it to the appropriate number of significant figures. 8. Look at the result – is it reasonable? Does it agree with a rough estimate? 9. Check the units again.

24. Page 40 # 19 A sports car moving at constant speed travels 110m in 5.0 seconds. If it then brakes and comes to a stop in 4.0 seconds, what is the acceleration in m/s 2 ? Express the answer in terms of "g's", where 1.00g=9.80m/s 2.

25. Programming the Quadratic Formula into your Graphing Calculator Utube Video http://www.youtube.com/watch?v=z1jqegs r7dMhttp://www.youtube.com/watch?v=z1jqegs r7dM Text Directions http://math.arizona.edu/~krawczyk/Calcula tor/TI83PLUS/TI83PQF.htmlhttp://math.arizona.edu/~krawczyk/Calcula tor/TI83PLUS/TI83PQF.html

26. Page 40 #21 A car accelerates from 13m/s to 25 m/s in 6.0 s. What was its acceleration? How far did it travel in this time? Assume constant acceleration.

27. Page 40 #22 A car slows down from 23 m/s to rest in a distance of 85 m. What was its acceleration, assumed constant?

28. Elaboration Activity Graph Matching D vs. T – groups of 3 to 4. Results can go on the hand out. Directions: Type in the following addresses and answer the questions in complete sentences in your notebook binder. http://www.physicsclassroom.com/mmedia/kinema/avd.cfm Describe the acceleration in the simulation. Be sure to explain what happens to acceleration when velocity changes. http://www.physicsclassroom.com/mmedia/kinema/acceln.cfm Observe the animation and answer the three questions with your group and check your responses. Which question(s) did your group have difficulty answering? Accelerated Motion Problems – complete individually when finished with activity.

29. Review of Motion in 1 Dimension (If time permits) Maze Game

30. Homework Chapter 2 Problems #s 16, 18, 23, 27, 32

31. Closure What conclusions can you make from examining the graphs below?