Transcript Lecture: Chapter 1 and Introduction to Vectors

If you can’t explain it simply, you don’t understand it well enough.
-Albert Einstein
If you thought science was certain – well, that is just an error on your part.
-Richard Feynman
What is Physics?
 It is the study of the basic nature of matter and the
interactions that govern its behavior.
 It is the MOST fundamental of the sciences.
 Its principles and theories can be used to explain the
fundamental interactions involved in chemistry, biology,
and other sciences at the atomic and molecular level.
Steps in the Scientific Method
 Careful observations of natural phenomena
 Formulations of rules or empirical laws based on
generalizations from these observations and experiences
 Development of hypotheses to explain the observations
and empirical laws and the refinement of those hypotheses
into theories
 Testing of hypotheses or theories by further
experimentation or observation
Units
 SI (Le Systeme Internationale d’Unites) units are used in the
scientific community in the United States
 This is otherwise known as MKS units (meters, kilograms,
seconds)
 Length is given in meters (One meter is the distance traveled
by light in a vacuum during 1/299,792,458 of a second, this is
the equivalent of defining the speed of light as 299,792,458)
 Mass is given in kilograms (One kilogram is the mass of the
international standard kilogram, a polished platinum-iridium
cylinder stored in Paris)
 Time is given in seconds (One second is the time required for
9,192,631,770 oscillations of the radio wave absorbed by the
cesium-133 atom)
Prefixes
Prefix
Power of 10
Abbreviation
femto-
10-15
f
pico-
10-12
p
nano-
10-9
n
micro-
10-6
μ
milli-
10-3
m
centi-
10-2
c
kilo-
103
k
mega-
106
M
giga-
109
G
terra-
1012
T
Unit Conversions
Multiplying expressions by one does not change its value. Similarly,
a conversion of 2 feet to meters would be
Significant Figures
 To state our knowledge of a particular number precisely, we
use significant figures:
Example:
0.00620 = 6.20 x 10-3
1.
2.
3.
Notes:
The leading three zeros locate the decimal point, but are not
significant in and of themselves.
The number of significant figures does not equal the number of
decimal points.
Changing units shifts the decimal point but does not change the
number of significant figures.
Using Sig Figs
 When multiplying or dividing several numbers, or taking roots,
the number off significant figures in the answer should match
the number of significant figures of the least precisely known
number used in the calculation.
 When adding or subtracting several numbers, the number of
decimal places in the answer should match the smallest number
of decimal places of any number used in the calculations.
 Exceptions:
It is customary to keep one extra significant figure if (and only if)
the number starts with a 1.
2. It is acceptable to keep one or two extra digits during intermediate
steps of a calculation, as long as the final answer is reported with
the proper number of significant figures.
Textbook problems in science and engineering use an accepted
standard of three significant figures for nearly all calculations.
Use scientific notation in your calculators at all times.
1.
Question 1:
Convert the following to SI units:
1.
9.12 μs
2. 3.42 km
3. 44 cm/ms
4. 80 km/hour
Question 2:
Convert the following to SI units:
1.
1 hour
2. 1 day
3. 1 year
4. 32 ft/s2
Question 3:
The quantity called mass density is the mass per unit
volume of a substance. Express the following mass
densities in SI units:
1.
Aluminum, 2.7 x 10-3 kg/cm3
2. Alcohol, 0.81 g/cm3