PHYSICS 101
(Physics for the Nonscientist)
Dr. Anatoli Frishman
frishman@iastate.edu
Web Page: http://course.physastro.iastate.edu/phys101/
1
Introduction
•What is physics?
•A science
•A basic science
•The most basic science
•Discovered by several generations of scientists
•Physics and measurements
•Relationships between experiments and theory
•Mathematics - language of science
Course organization
•Lectures
•Homework
•Exams (multiple choice)
•two midterm exams and a comprehensive final exam
•Formula sheet
•Syllabus
2
Physical quantities, units and standards
What do we measure? - Physical quantities.
Units - a unit is a measure of the quantity that is defined to be exactly 1.
Examples: meter, mile, gram, kilogram.
Standard - a reference to which all the other examples of the quantity
are compared.
Base quantities, and their standards.
The International System of Units (metric system)
Quantity Unit name Unit symbol Standard
Length
Meter
m
Distance traveled by light in
1/299,792,458 second
Time
Second
s
Time required for 9,192,631,770 periods
of radiation emitted by cesium atoms
Mass
Kilogram
kg
Platinum-iridium cylinder in
International Bureau of Weights and
Measures at Sevres, near Paris
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Other systems of units
•CGSE System of Units (metric system):
centimeter, gram, second
1m = 100cm
1kg = 1000g
•British engineering system
This system has force instead of mass as one of its basic quantities,
which are feet, pounds, and seconds.
1 m = 3.281 ft; 1 inch = 2.54 cm
1 kg = 0.06585 slug (Not the same as weight!)
on Earth 1 kg weighs 2.205 lb, on the Moon 1 kg weighs 0.368 lb
4
Multiples of Units
10-24
yocto-
y
10-21
zepto-
z
10-18
atto-
a
10-15
femto-
f
10-12
pico-
p
10-9
nano-
n
10-6
micro-

10-3
milli-
m
10-2
centi-
c
103
kilo-
k
106
mega-
M
109
giga-
G
1012
tera-
T
1015
peta-
P
1018
exa-
E
1021
zetta-
Z
1024
yotta-
Y
Conversion of units:
Multiply by the appropriate representation
of 1 to cancel the unwanted units away
Converting between metric units is easy,
as it only involves powers of 10.
Example 1: Convert 3kg into gram
1000g
3kg  3kg
 3000g
1kg
Example 2: Convert 10 mph into m/s
10
mile
mile
1h
1609 m
 10



h
h
3600 s 1 mile
 4.47 m/s
5
Measurements and uncertainty
When we measure something, there’s a limited accuracy:
result  error (or accuracy)
Example 1:
2.35  0.01
Example 2:
Wrong: 2.35  0.1
Correct: 2.4  0.1
Significant figures
Example 1:
0.24630
1sf
2sf
3sf
4sf
5sf
0.2
0.25
0.246
0.2463
0.24630
Example 2:
Not so clear in some cases: 200 (1,2,3 ?)
Scientific notation is crystal clear:
2  102 (or 0.2  103)
2.0  102 (or 0.20  103)
2.00  102 (or 0.200  103)
1sf
2sf
3sf
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Physics
Mechanics Thermal properties
Electromagnetism
•Electrostatic
•Electric current
•Magnetism
Condensed Mater
High energy
Optics
Atoms & particles
•Geometrical optics
•Wave optics
Biophysics
Classical physics
Quantum physics
Relativistic physics
Quantum relativistic physics
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MECHANICS
KINEMATICS
Kinematics is the study of motion, without the investigation of the cause of the motion
1. Motion
•Motion of what?
Material point
(An object with an irrelevant dimension for the purposes of a particular problem)
•Development of models
Example: linear motion versus rotational
•Motion is relative to the object of reference
Examples: the motion of an airplane passenger relative to the airplane, or the
motion of an airplane passenger relative to the ground.
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2. One dimensional (1D) uniform motion
(Motion along a straight line with a constant speed)
Example:
Time interval:
Distance:
Speed:
t  t final  tinitial  2s
d  d final  dinitial  10m
d
v

t
10 m
v
 5m / s
2s
d  vt  5m / s 2s   10m
If tinitial  0 and dinitial  0,
then t  t final  t and d  d final  d
d  v t
Note: In science, the capital Greek letter Δ means difference.
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3. Speed
a) Average speed:
Definition:
d d final  dinitial
v

t
t final  tinitial
(total distance
over total time)
b) Instantaneous speed:
Definition:
d
v  lim
t 0 t
Question: If the average speed is non-zero over some time interval, does this
mean that the instantaneous speed is never zero during the same interval?
A) Yes
B) No
C) It depends
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Example 1
Given:
A
d1
d 2
B
AB  d  100km
x
d1  d 2 
 50km
2
v1  40km /h
Formula used:
d
v
t
v2  60km /h
v ?
Solution:
t1 
d1
50km
5

 h;
v1
40km /h 4
t 2 
5
5
25
h  h
h
4
6
12
d
100km
v

 48km /h
t 25 / 12h
d 2
50km
5

 h
v2
60km /h 6
t  t1  t 2 
Answer:
v  48km /h
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Example 2
Given:
Formula used:
t1  t 2  1h
d
v
t
v1  40km /h
v 2  60km /h
v ?
Solution:
d1  40km
d 2  60km
d  d1  d 2  40km  60km  100km
t  2h
d 100km
v

 50km /h
t
2h
Answer:
v  50 km/h
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