Unit 1

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Oct 24, 2013 (3 years and 10 months ago)

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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
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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
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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
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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
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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
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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
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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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10

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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11

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
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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
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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
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14

Unit 1 Appendix

Unit
1
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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
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3 Photo and Clipart:
Microsoft Clipart Collection, reproduced under general license for educational
purposes.