1. Relative Velocity Pre-Class Friday 1-13-12
Garfield is walking at 1 m/s, but the wind is blowing him at -3 m/s. What velocity does Jon think he has?

2. Chapter 3: Accelerated Motion
Uniform motion: constant speed or velocity
Nonuniform motion: changing speed or velocity

3. Measuring velocity (in meters per second, m/s)
Velocity interval is defined as:
Δv = vf - vi
The i is initial and the f is final
D (Greek letter “delta”) stands for “change in” or final - initial

4. a: average acceleration (m/s2)
Acceleration is the measure of the change in velocity over a given time
Constant velocity means no acceleration Dv
a = Dt
a: average acceleration (m/s2)
v: velocity (m/s)
t: time (s)

5. Velocity-Time graph Similar to Position-Time graph
Displays the velocity of an object at any time
Slope of the line shows the average acceleration

6. Pre-Class for Tuesday 1-17-12
All of the following can be found on a velocity-time graph except for:
Average acceleration
Inertia
Velocity
Time

7. vf = vi + a t x = vi t + 1/2 a t2 vf2 - vi2 = 2 a x x = (vf + vi) t/2
EQUATIONS OF MOTION
vf = vi + a t
x = vi t + 1/2 a t2
vf2 - vi2 = 2 a x
x = (vf + vi) t/2

8. Pre-class for Wednesday 1-18-12
Section
Pre-class for Wednesday
3.2
A car is moving with an initial velocity of vi m/s. After reaching a highway, it moves with a constant acceleration of a m/s2, what will be the velocity of the car after traveling for t seconds?
vf = vi + at
vf = vi + 2at
vf2 = vi2 + 2at
vf = vi – at

9. ACCELERATION BY GRAVITY
The Earth constantly accelerates all objects towards its center
We use the variable g for the acceleration of gravity
g = 9.8 m/s2
a = - g = m/s2
(different from book)

10. Taking a closer look…

11. vf = vi - g t y = vi t - 1/2 g t2 vf2 - vi2 = - 2 g y
EQUATIONS OF MOTION
vf = vi - g t
y = vi t - 1/2 g t2
vf2 - vi2 = - 2 g y

12. m/s
m; yes, m/s s
m/s, -310 m
m/s, -20 m
m/s
m, 10.8 m/s m
m/s2, 29g
x108 m/s2, 11ms m
m/s,-10 m, 20 m
CHAPTER 3
m/s2
m/s
m/s2, 0 m/s2, -2 m/s2, -4 m/s2
85. Car B,Car A&C tie
m/s, 1.83 mach
m, 43.2 m
138m, 550m m

13. What is the accepted value for the acceleration of gravity?
Section
3.2
Pre-class Thursday
What is the accepted value for the acceleration of gravity?

14. FALLING LAB Materials: Objective:
6 pennies
stop watch
meter stick
tape
Objective:
determine the acceleration of gravity
Each group will turn a paper into me today.

15. PROCEDURES Stack five pennies and tape them together.
Drop the five pennies from 3 different heights.
Measure the distance fallen and the time it took to fall to the ground.
Determine the acceleration of gravity.
Repeat the experiment for the single penny.
Complete the chart on the next slide and answer the questions.

16. FILL OUT THE CHART Questions
Find the percent difference between your answer and the accepted answer.
How could you improve your results (at least 2 examples)?

17. vf = vi + a t x = vi t + 1/2 a t2 vf2 - vi2 = 2 a x
EQUATIONS OF MOTION
vf = vi + a t
x = vi t + 1/2 a t2
vf2 - vi2 = 2 a x

18. Pre-class Thursday
Write:
“Review 4 test”

19. TEST OVER CHAPTER 3
Take a few minutes to review/finish pre-class problems.
You need your own paper.
Do not write on my paper.
Box in final answers.
Write clearly.
You may need a calculator.