Unit 1
Units and Measurements
© 2006, B.J.
Lieb
Giancoli
,
Sec. 1

1
1

8
What is Physics ?
Studies Fundamental Forces in Nature
Gravity
Electricity &
Magnetism
Strong
Nuclear
Weak
Nuclear
Studies Small and Large Systems
Unit 1

02
Subfields of Physics ?
•
Includes
; acoustics, astrophysics, atomic physics, cryogenics,
electromagnetism, elementary particle physics, fluid dynamics,
geophysics, mathematical physics, mechanics, molecular physics,
nuclear physics, optics, plasma physics, quantum physics, solid
state physics, statistical mechanics, thermodynamics
.
Unit 1 03
CAT Scan
Brain
X

Ray
Medical Applications
Sonogram
MRI
Topics Covered in PHYS 243
•
Classical Mechanics
•
Fluids
•
Vibrations and Waves
•
Sound
•
Thermodynamics
Unit 1

04
Measurement Uncertainty
In lab you will have to
estimate the uncertainty in
any measurement. The
result might be
X
=8.8 cm
±
0.1cm
Another way to show
uncertainty is the number
of significant figures
–
the
number of reliably known
digits, which might be two
in this case.
Unit 1

05
Significant Figures
•
0.0034 has two significant figures
•
44.58 has four
•
800 has one, 8.00x10
2
has three
•
Multiplication
or D
ivision:
the final
result should
have only as
many digits as the number with the least number of significant
figures used in the calculation.
23.66
x 1.1 =
26.03=26 (two)
•
Addition
or
Subtraction
:
the final
result is
no more accurate
than the least accurate number used.
23.5 + 43.2 + 44 = 110.7 = 111
Unit 1

06
Significant Figures
in Mastering Physics
•
Mastering Physics (MP) is very strict and intolerant about significant.
Most problems expect three significant figures. Fortunately you can answer
every question 20 times.
•
MP
advises students to carry the full precision on intermediate results until
they obtain the final answer. They should apply their rounding rules only on
the final answer.
•
When the student's answer is within tolerance of the full

precision answer,
the score is not penalized, the number of wrong answers is not
incremented, and the feedback reads: "Very close. Check the rounding and
number of
significant
figures
in your final answer."
•
When the student's answer is further off, but still within a looser tolerance
of the full

precision answer, the score is penalized, the number of wrong
answers is incremented, and the feedback reads: "Not quite. Check through
your calculations; you may have made a rounding error or used the wrong
number of
significant
figures
."
Unit 1

07
5. Units, Standards and SI System
Length: 1 meter
defined as the distance light travels in
1 / 299,792,458 of a second.
Mass: 1 kilogram
defined as a
standard mass
of a certain
cylinder kept near Paris
Unified Atomic Mass: 1 u
defined as the 1/12 of the mass of
the
12
C atom.
1u = 1.6605 x 10

27
kg
Time: 1 second
defined by a cesium clock.
Unit 1

08
Metric Prefixes
You Must
Know
giga
G
10
9
mega
M
10
6
kilo
k
10
3
centi
c
10

2
milli
m
10

3
micro
10

6
nano
n
10

9
pico
p
10

12
femto
f
10

15
Unit 1

9
Math Symbols You Must Know
x > y
x
is greater than
y
y < x
y
is less than
x
y << x
y
is much less than
x
y
x
y
is approximately equal
x
y
x
y
is defined equal to
x
x
change in
x
Unit 1

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Converting Units
•
You are strongly urged to use the standard way of doing
units conversion in physics. It reduces errors and is much
easier for the grader to check.
•
It is based on the fact that you can multiply anything by ‘1’
without changing its value.
Example:
1 inch = 2.54 cm Thus
Example:
The area of a surface 5.0 in by 3.0 in is
Unit 1

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Order Of Magnitude Estimate
•
It is a good idea to do a rough estimate before doing a
detailed calculation
•
Then when you work the problem, ask yourself if the
result appears reasonable.
Unit 1

12
Dimensions and Dimensional Analysis
•
In order to be correct, an answer must have the correct
units.
•
Your solution must include units to show how they
work out
•
You can often use units to guide you to the answer.
•
Useful Rule: We can add or subtract quantities only if
they have the same dimensions.
•
Example:
Each term must have units of length.
Unit 1

13
Math Review
•
I have created two review tutorial/quizzes in Mastering
Physics:
•
Algebra Review
–
needed for Unit 2 (Chapter 2)
•
Trigonometry Review
–
needed for Unit 5 (Chapter 3)
•
These count the same as a homework. The deadline is
extended but you need to know the material ASAP.
•
Appendix A has an excellent summary of the math you
need for this course. You must understand all of the
material in Appendix A

1, A

2, A

3, A

4 and A

7.
Unit 1

14
Unit 1 Appendix
Unit
1

15
Photo and Clip Art Credits
Some
figures electronically reproduced by permission of Pearson Education, Inc., Upper
Saddle River, New Jersey
Giancoli
, PHYSICS,6/E
© 2004.
Slide
1

2 Photos and Clipart: Microsoft Clipart Collection, reproduced under general license for educational
purposes.
1

3 Photo and Clipart:
Microsoft Clipart Collection, reproduced under general license for educational
purposes.
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