1. Class Notes 02 September Turn in HW / Pick up HW! Today:
Draw origin / coordinate system
Did you write the general eqn’s??
#1b: The car did not decelerate
Today:
One more f.f. example problem
Graphical Methods
Vectors

2. How many of the “fundamental four” equations can you remember?
0  1 2 3
4  5

3. Example
A rocket is traveling upwards at m/s. When it is 500. m above the Earth its booster turns off. How high above the Earth does the booster go? How long until it hits the ground?
Part b) is solved easiest using x = x0 + v0t +(1/2)at2. Solving quadratic gives two solutions. Discuss the erroneous (non physical) answer.
1010. m, s
– 4.15s

4. Velocity at t = 2 s? So now we’ll zoom in (t = 1-3 s)
Write velocity equation, with lim t0

5. Velocity at t = 2 s? Zoom in again (t = 1.9-2.1 s)
Ave vel = Slope = … = –12 m/s

6. Ave vel is nearly constant!
Velocity at t = 2 s?
Slope = … = –13 m/s
Ave vel is nearly constant!
Notice Dt  0
the definition of instantaneous velocity, v = lim(x/t), can be written v = lim(vave).

7. Summarize Secant line slope gives average velocity
Tangent line slope gives inst. velocity

8. Constant acceleration
On a v-vs-t graph, I want to draw various situations where the acceleration is constant.
For each I want you to think of a physical example that could be like that.

9. Constant acceleration
I predict that some of these will be drawn.

10. Graphical Acceleration
Consider vel-vs.-time graphs
In much the same manner, the slope of the straight line connecting two points on a velocity-vs.-time curve gives the average acceleration.
The slope of the tangent line gives the instantaneous acceleration
Argue again with slope = rise/run = v/t, which is by definition the average acceleration. Similarly with the instantaneous acceleration.

11. Displacement from graph
Consider a vel-vs.-time graph:
The area under ANY velocity-
vs.-time curve (between t1
and t2) is the displacement
during that time interval. v v t t1 t2 v t t1 t2

12. Considering the test, which describes you?
I feel very confidant
I’ll do well
I’ll be OK
I’m a bit worried
I’m very worried
I think I’ll sleep in

13. Considering the test, what grade do you expect?
High A
Low-Mid A
High B
Low-Mid B
High C
Low-Mid C
Failure

14. Oh joy! Our first test! 8:00 class arrive 5 min early
No cell phones! Cell phone=0
55 minutes.
~1 page short answer (35-40%)
3 of 4 problems (60-65%)
Work directly on the test paper
Review sheet
Online resources

15. Homework Read chapter 3.1-3.3 Homework on Canvas coming soon
TEST WEDNESDAY (50pts)
All of Chapter 1 and 2
Review sheet
Practice quizzes, Old tests
Know, not memorize, the funda- mental four equations!