Welcome to Physics 100 !!!!
Dr. Gregory G. Wood
Fall 2005
A bit about me….
Just joined CSUCI
Married to Dr. Tabitha Swan-Wood
Expecting a baby girl Jan. 15, 2005
Quiz
1) What is your name?
2) What is your major?
3) What is the email address you would like
correspondence about this course sent to?
4) Why are you taking physics? (Try to put something
more than “because I have to…”)
5) Tell me a bit about yourself.
What is Physics?
Broadly defined: A scientific method
used to explain physical phenomena in
the universe using the tools of
mathematics.
Examples of Physics…
Classical Mechanics:
Motion of the planets
1-D Atomic Chain Transverse Modes-Java Applet
Examples of Physics…
Light & Waves:
Rainbows & Prisms
Ultra-Sounds
Examples of Physics…
Light & Waves:
Atomic Scale Imaging
Examples of Physics…
Quantum Mechanics & Solid State:
Transistors and Solid Electronics
Physics Permeates Your Life
TV
Radio
Computers
Automobiles
Plasma Screens
Medical Instruments: MRI, Ultrasound,
X-rays,…
Chapter 1
Skim Chap. 1 and make sure you
understand it.
Important prefixes:
Power Prefix Abbreviation
103 kilo k
10-2 centi c
10-3 milli m
10-6 micro m
Chapter 1
Dimensional Analysis:
Units must be equal on both sides of an
equation
[units] = [units]
When adding or subtracting units must be equal
[units] + [units]
Examples
Yes: 5 m/s = 3 m/s + 2 m/s
No: 5 m/s = 3 m/s2 + 2 m/s
Chapter 1
Scientific Notation
3,240 = 3.24 x 103
Converting Units
To convert 23 seconds to units of hours:
23 sec x 1 min x 1 hour = 0.00639 hr = 6.39 x 10-3 hr
60 sec 60 min
Chapter 1
How to Approach Physics Problems:
Carefully read the problem
Visualize the problem
Sketch a diagram of what’s happening
If complicated, try to separate the events
Set-up the appropriate physics equations
Solve the equations
Check your answer: units and magnitude
Think about your answer
Chapter 1
A note on grading and partial credit
Give a solid attempt at every problem
Sketches will be worth something
Chapter 1
Distance vs. Displacement
Chapter 2
Position & Displacement…
Create an axis
0m position 6m
At t=0sec Marm is at 0m and at t=3sec Marm is
at 6m
Total Displacement (6m-0m) = 6m
Total Time (3sec-0sec) = 3sec
Chapter 2
0m position 6m
At t=0sec Marm is at 0m and at t=3sec Marm is at 6m
Total Displacement (6m-0m) = 6m
Total Time (3sec-0sec) = 3sec
Average Speed
Average Speed = Total Displacement = 6m = 3m
Total Time 3 sec sec
Average Velocity
Equals average speed plus a direction 3m
To the right
sec
Chapter 2
Slope of tangent line = instantaneous velocity
Position vs. Time
Time [sec] Position [m]
0.8 1
2 2.2
4 3
6 3.5
Average Velocity:
between t=0 sec and t=6 sec
Instantaneous Velocity:
at t=6 sec
Chapter 2
Instantaneous Velocity
Lim Dx Dx
Dt0 Dt
Dt
Dx
Dt
Chapter 2
Average Acceleration
Dv v f vi
aave
Dt t f ti
Instantaneous Acceleration
Dv
a Dt0
lim
Dt
Units:
Dv m/s = m
Dt s s2
Chapter 2
Negative Acceleration (Deceleration)
a +
v
Dv v f vi
vf < v i because aave
Dt t f ti
Chapter 2
Motion under Constant Acceleration
Useful Equations:
v v0 at ( 2 7)
1
vav ( v0 v ) ( 2 9)
2
1
x x0 ( v0 v )t ( 2 10)
2
1
x x0 v0t at 2 ( 2 11)
2
v 2 v0 2a ( x x0 )
2
( 2 12)
Constant Accleration
Aspen the dog starts at 2.0 m/s and
dv Dv
a lim Dt 0 accelerates at 3.3 m/s2 for 1.1 s before
dt Dt reaching top speed. What is her top speed?
v f v0
a Vf=2.0 m/s + 3.3 m/s2 x 1.1s = (2.0+3.63)m/s
t = 5.6 m/s (two sig figs).
v f v0 at ( 2. 7 )
v vs. t
at
A1=½ t * at
A2=v0t
t
v vs. t for Constant Acceleration
Distance = Area under v vs. t curve
(because d = v*t)
at
d = A1 + A2
A1=½ t * at
d = v0t + ½ t * at
x – x0 = v0t + ½ at2
x = x0 + v0t + ½ at2 (2-11) A2=v0t
t
How far?
Distance is the area under the
Velocity vs. time graph thus:
Aspen the dog starts at 2.0 m/s and
1 accelerates at 3.3 m/s2 for 1.1 s before
d v0t att reaching top speed. How far does
she travel?
2
D = area rectangle + area triangle
Area triangle = ½ base x height
1 2
x x0 v0t at (2.11)
2
Position vs. Time Plots
Constant Acceleration
Constant Velocity 1
x x0 v0t at 2
2
a = b + ct + dt2
Upward Parabola
Constant Deceleration
a = b + ct – dt2
Downward Parabola
Larger slope equals larger velocity
Without time information…
v f v0 at ( 2 .7 )
1 2
x x0 v0t at (2.11)
2
Solve (2.7) for time and substitute into (2.11) and you will find:
v v 2a( x x0 )
2
f
2
0 (2.12)
Aspen goes from 2.0 m/s to 5.6 m/s over a distance of 4.2 m,
find acceleration.
Chapter 2
Example 1 (prob. #12)
It was a dark and stormy night, when
suddenly you saw a flash of lightening.
Three-and-a-half seconds later you heard
the thunder. Given that the speed of
sound in air is about 340 m/s, how far
away was the lightening bolt?
Chapter 2
Example 2 (prob. #40)
When you see a traffic light turn red you
apply the brakes until you come to a sop.
If your initial speed was 12 m/s, and you
were heading due west, what was your
average velocity during braking?
Assume constant velocity.
Chapter 2
Example 3 (prob. #100)
You drop a ski glove from a height h onto
fresh snow, and it sinks to a depth d
before coming to rest. (a) In terms of g
and h, what is the speed of the glove
when it reaches the snow? (b) What are
the magnitude and direction of the
glove’s acceleration as it moves through
the snow, assuming it to be constant?
Give your answer in terms of g, h, and d.
Lab One Activity: Measure a
4-setups: measure time and distance
Assume constant acceleration
Each group uses different angle of
incline
Use a variety of distances – average
all a values
Rest login to MP website/homework