1. Honors Physics 28 Sept 09 Today: Intro to on-line text and acceleration Homework: Read section 2.2 p 48-59 Text address: http://my.hrw.com Tomorrow: We will derive the equations of motion presented in this section in class If you need a hard copy of the book – please let me know – you can get one in class, or see me after (or before) school

2. Acceleration (p 48-49) Acceleration is the rate of change of velocity with respect to time a avg = Δv/Δt = (v f –v i )/(t f -t i ) Notice how this form looks similar to that of velocity (Δx/Δt) Just as the slope of x vs t is velocity, the slope of v vs t is acceleration!!

3. Quick math questions A car can accelerate at a rate of 2m/s 2. How long will it take for the car to reach a speed of 30 m/s? What is the rate of acceleration for a car that slows from 30 m/s to a stop in three seconds?

4. Honors Physics 29 Sept 2009 Today: deriving the equations of motion – Check out the new assignments that are posted on the wiki – Make sure the entire derivations we do together in class are in your notebook!! – Homework: work on assignments

5. Variables of linear motion d = displacement (Δx) t = time of travel (Δt) a = rate of constant acceleration v i = initial velocity v f = final velocity

6. Definitions of linear motion v avg = Δx/Δt a avg = Δv/Δt

7. Honors Physics 30 Sept 2009 Today: Using the equations of motion and the logical problem solving approach Homework: Section review, page 59 – answer in composition books Notebook check on Friday

8. Key Steps in Problem Solving Identify what you are looking for Identify what you know (state your variables) Identify the equation(s) you need from the variables you have (and don’t have) Rearrange equations to solve for the unknown Fix any unit issues Plug and chug Check your units

9. Practice # 1 A car travelling at 10.0 m/s accelerates at a rate of 2.5 m/s 2 to a final velocity of 20. m/s. How long does it take for this to occur?

10. Practice # 2 A plane must reach a speed of 100 m/s at take off. If it takes 10 seconds to get down the runway, how long does the runway have to be?

11. Practice #3 Upon lift off, a rocket ship accelerates at a rate of 1 m/s 2. How fast is it travelling when it reaches a height of 10,000 m?

12. Honors Physics 1 Oct 09 Today: Independent time to work on assignments – please check out the new assignments posted on the wiki Homework: Continue assignments – Notebook check tomorrow – Don’t forget your composition book.

13. Honors Physics 2 Oct 2009 Introduction to free fall Warm up question: If something accelerates from rest at a rate of 10 m/s 2, how fast is it travelling after 5 seconds? Homework: – Read section 3 in chapter 2 (p60-65) Next week: Free-fall lab work

14. Theory behind the lab We know:d = v i t + ½ a t 2 If you drop something, v i = 0, so the equation reduces to:d = ½ at 2 If you rearrange with a on the left you get a = 2d/t 2 This lets you find the acceleration of an object due to gravity!! You can also determine the slope of a graph of v vs. t to get a. We will do this too.