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
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 60 sec 60 min
= 0.00639 hr = 6.39 x 10-3 hr
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
0 m 6 mposition
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
0 m 6 mposition
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
Average Velocity Equals average speed plus a direction Total Time
= 6m = 3 m3 sec sec
sec3 m
To the right
Chapter 2
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
Slope of tangent line = instantaneous velocity
Chapter 2
Instantaneous Velocity Lim x
t0 t
tx
tx
Chapter 2
Average Acceleration
Instantaneous Acceleration
Units: v
if
ifave tt
vv
t
va
t
va
limt0
tm/s
sms2 =
Chapter 2 Negative Acceleration (Deceleration)
vf < vi becauseif
ifave tt
vv
t
va
v a +
Chapter 2
Motion under Constant Acceleration Useful Equations:
)122()(2
)112(2
1
)102()(2
1
)92()(2
1
)72(
020
2
200
00
0
0
xxavv
attvxx
tvvxx
vvv
atvv
av
Constant Accleration
)7.2(
lim
0
0
0
atvvt
vva
t
v
dt
dva
f
f
t
Aspen the dog starts at 2.0 m/s andaccelerates at 3.3 m/s2 for 1.1 s beforereaching top speed. What is her top speed?
Vf=2.0 m/s + 3.3 m/s2 x 1.1s = (2.0+3.63)m/s= 5.6 m/s (two sig figs).
v vs. t
A1=½ t * at
A2=v0t
at
t
v vs. t for Constant Acceleration
A1=½ t * at
A2=v0t
at
t
Distance = Area under v vs. t curve(because d = v*t)
d = A1 + A2
d = v0t + ½ t * at
x – x0 = v0t + ½ at2
x = x0 + v0t + ½ at2 (2-11)
How far?
atttvd2
10
Distance is the area under theVelocity vs. time graph thus:
D = area rectangle + area triangle
Area triangle = ½ base x height
)11.2(2
1 200 attvxx
Aspen the dog starts at 2.0 m/s andaccelerates at 3.3 m/s2 for 1.1 s beforereaching top speed. How far doesshe travel?
Position vs. Time Plots
200 2
1attvxx
Constant VelocityConstant Acceleration
Constant Deceleration
a = b + ct + dt2
a = b + ct – dt2
Upward Parabola
Downward ParabolaLarger slope equals larger velocity
Without time information…
)11.2(2
1 200 attvxx
)7.2(0 atvv f
Solve (2.7) for time and substitute into (2.11) and you will find:
)12.2()(2 020
2 xxavv f
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