Physics
Dr. Fisher
The International School of
Minnesota
2013
…about me
• Farm boy from central Iowa: cattle, hogs, corn,
soybeans, alfalfa, brothers, machinery, outdoors,
sports, school, drama, music, JETS
• BS Chemical engineering Iowa State, 3M, pilot
• MS biomedical engineering, campus politics
• PhD (Bio)chemical engineering Iowa State (minor
in Technology and Social Change)
• Prof at U. of Washington (Seattle) in Chem Engr
• Research engineer and scientist and manager at
Cargill Inc., fermentation technology, separations,
Brussels
• Married, kids, bees, hobbies, rants, likes,
dreams……
Some class logistics
• Course overview: handout (lots of info!)
• Name on book!
• Ismscience.org
– Subscribe to get updates
– Check weekly
– Check before you sit to do HW (might be hints or
changes)
• Come see me for 5 min
– Why physics class, math you’re in, legos, other
classes, grade expectation, what your parents do.
How long are these things?
How to lie with numbers
• 3 miles + 20 inches = 3.000316 miles (Y or N)
• A truck weighs 3560 pounds. You pick up 4
tons (1 ton = 2000. lbs) of rock from Rocks-RUs. You weigh 130 pounds and hop in and
drive over a scale. What will the scale say?
Handling numbers: significant figures
• Write them any way you want, but please
don’t misinform others about their precision!
• Pre-Exercise: measure table top area and
report only the sig figs you can justify
• You should have sig fig knowledge from
Biology, do you remember?
Reading notes
• Assigned for Monday
• Turn in 1 page of notes that capture the main
points of the section
• This will help you learn, prep you for college,
and show me you ready for class
• 1st assignment is due next Tuesday, chapter 1,
sections 1-7
In Physics, numbers describe real
things
• There are always limits to how precisely we
can measure something.
• So we have to learn to write the numbers to
reflect that precision
• And we need to learn to + - x / those numbers
correctly
Some numbers are known perfectly
well
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Examples?
Pi
whole numbers: appear in equations
Zero
Definitions (1.54cm/inch is a definition)
Others?
The sig fig (significant figures) rules
• Zeros count when…
– Between numbers
– After numbers and after decimal
– After numbers in front of decimal
40056
3.9000
162000.
• Zeros don’t count when
– After decimal but not after number
– After number with no decimal
– Alone before a decimal
0.0036833
23,000
0.00020
• When multiply and divide, the sig fig of the answer is the
least of the sig figs of any input
• When add or subtract, the sig fig of the answer can be
found by logic
• You have to know or find how many sig figs certain
constants or conversions have ( p, 2, square root)
1-4 Measurement and Uncertainty;
Significant Figures
Calculators will not give you the right
number of significant figures; they usually
give too many but sometimes give too few
(especially if there are trailing zeroes after a
decimal point).
The top calculator shows the result of 2.0 /
3.0.
The bottom calculator shows the result of
2.5 x 3.2.
Sig fig practice (homework)
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4.55 x 99,345 =
0.002/0.041 =
88.4 cm x 1.2m =
7.22 x 103 / 0.22 =
5210 + 3 =
5.23/p =
Radius = 3.55m/2 = ______; 3.55m is diameter
You have been learning physics for 1516 years
• ..\start of year materials\how we learn
physics.pptx
Learning physics – some advice
To succeed in this course you will need to learn the material at
three different levels.
(i) the basic facts. You will be able to do some problems using
just these basic facts, but facts are not enough…..
(ii) You will learn problem solving techniques . This is like
learning to solve a puzzle or play a game. I will teach you
some rules that work, and you have to practice.
(iii) You will learn to use your reasoning skills. If you approach
Physics as reasoning based on a few basic facts and
procedures, this course will be much easier than if you try to
memorize how each problem is done.
How to take notes in physics
• Should I write everything that’s
presented?
• Should I just listen and use the slides?
• Should I close my eyes and achieve a Zen
state of physics?
Taking class notes: intelligent notes
1. My words to explain the slides: title of slide,
my comments
2. Notes on the board: connect to slide
3. Demos in class (3-D, real life): sketch, brief
notes
4. Problems solved on the board. It’s good to
write the solution down again
5. Write the section numbers of book that we
discuss
6. Helpful comments from students
Accuracy vs precision
https://www.youtube.com/watc
h?v=_LL0uiOgh1E
How could you be more accurate in measuring
the table top?
How could you be more precise in measuring the
table top?
Quiz: fill in the letters that apply
1. Zeros count as a sig fig when:
2. Zeros don’t count when:
Position of zeros
a.
b.
c.
d.
e.
Alone before a decimal
After numbers in front of decimal
After number with no decimal
After decimal but not after number
After numbers and after decimal
f. Between numbers
g. I before e except after c
h. Zeros never count, they are zero!
The sig fig (significant figures) rules
• Zeros count when…
– Between numbers
– After numbers and after decimal
– After numbers in front of decimal
40056
3.9000
162000.
• Zeros don’t count when
– After decimal but not after number
– After number with no decimal
– Alone before a decimal
0.0036833
23,000
0.00020
• When multiply and divide, the sig fig of the answer is the
least of the sig figs of any input
• When add or subtract, the sig fig of the answer can be
found by logic
• You have to know or find how many sig figs certain
constants or conversions have ( p, 2, square root)
Demo/hands on
• Measure the area of the top of your table.
– Report in m2
– Be precise
– Be accurate
– Have one number for the group in 5 minutes
Handling numbers: units and
conversion
• Section 1-5: Units and the SI system
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Meter
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Second
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Kilogram
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a few more we’ll learn
• Converting numbers: the “fishbone” method
(not in book)
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Do problems 12 and 14 in class
Scientific notation—do you know it?
• Use of scientific notation allows us to avoid
writing lots of zeros
– Example: the temp of the universe just after the
Big Bang started it all =
• 100,000,000,000,000,000,000,000,000,000,000oK
• Easier to write 1032K
• You need to be able to convert between forms
– Use scientific notation
– or stretched out
6.0221415 × 1023
299 792 458 m / s
• Check: write each of these the other way.
How to check if your answer is
reasonable, or get a crude estimate
• “Order of magnitude estimate”
– Also called “back of the envelope estimate”
– OME is better than a SWAG
• Any input is good if it’s within an order of
magnitude.
– Is the length closer to 1m, 10m, or 100m?
– Is the mass 1g, 10g, or 1000g?
• Check: estimate the mass of all the HS
students together.
Look at HW
More practice with numbers
1. Calculate seconds per year.
2. How many human teeth are in this room
right now? (normal is 32 per adult, 28 per
teen)
3. (23,456 * p)3.5 =
You need to know what density is
• Density r is mass per volume
– Units are usually kg/m3, can be g/mL or g/cm3
• r = m/volume
• Find density for this man
– mass of 72kg
– Volume of 67.5L
• Calculator says 1.06666666666666666
Quiz for turning in
• Given info in the back cover, calculate the
mass of the air in this room: 5.5m x 8m x 3m.
Show all work.
• After you calculate the answer, show it
properly with sig figs.
• This will help me measure how well you
learned in class, how well you remember, and
how well you have mastered the fishbone
method of calculation.
1-5 Units, Standards, and the SI System
We will be working in the SI system, where the basic units are
kilograms, meters, and seconds (plus a few more)
Other systems exist:
US system or Imperial system; pounds, inch,
foot, yard, mile, seconds
cgs; units are grams, centimeters, and
seconds.
British engineering system has force instead
of mass as one of its basic quantities, which
are feet, pounds, and seconds.
1-5 Units, Standards,
and the SI System
These are the standard SI prefixes
for indicating powers of 10.
You should memorize T, G, M, k, c,
m, m, n
*Doing HW in physics
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Separate page to hand in
Name and date on page
Write problem number
Solve problem showing all work
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Draw a sketch if at all possible and label variables
What do you know
What do you need to find
Show equation without numbers (symbolic)
Fill in numbers and units
• Use fishbone method
– Box around final answer
• Does the answer make sense? If not, recheck, or
at least comment on it.
*Look at HW problems for practice
• Practice problems together
– The area of your book cover
– How many seconds in the day
• Problems 1:p-44
The basics
• What is science?
– A systematic process that builds and organizes
new knowledge in the form of testable
explanations and predictions about the universe.
– The knowledge of the physical or material world
gained through observation and experimentation.
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will we do science in this class?
will we learn science in this class?
We all can observe to gain new knowledge
Or we can accept knowledge from others
(dogma)
Focus on Physics
• What is physics? The study of the behavior
and structure of matter and energy
• Matter -- any substance that has both mass
and volume
• Energy – a quantity in some form that can be
“spent” or consumed to do work. (eg. Heat,
light, motion)
• (Build Topics Map of Physics)
Map of knowledge
All knowledge
Testable phenomena
Untestable beliefs
Topic map
*Using your text book
• Scan the chapter before you read it: headings,
pictures, graphs
• Scan the chapter before each class: emphasize
the sections that are coming
• Read and STUDY the sections after I discuss in
class
• Use example problems when you do the HW
• HW will tell you which section to focus on
• Check: open to the chapter answers
**Intro to lab safety
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Be responsible
Move slowly
Do not throw anything, do not wrestle or grab
You may retrieve equipment, ask if you don’t
know.
• Do not touch anything that is not part of your
lab.
• Put your things away at end
ISM Lab Safety Rules
a.
b.
c.
d.
No horseplay in the lab
No students may stand on chairs or tables
Students may not move chemicals from the lab
Eye goggles or safety glasses are required by all people in the lab for the
following conditions
i. Any heat source is in use
ii. Anyone is using any material (liquid, dry, or gas) that would be harmful
if put directly into an eye
iii.A pressure source (higher than a blown up balloon) is in use
iv.Activities are in the lab that could result in chips, shards, or any flying
objects, such as hammering, launching projectiles, etc.
e. Food in the labs
i. Food is not allowed in the lab (except water in bottles)
ii. Food can be allowed for planned special activities and with teacher
permission, but all table tops must be disinfected and wiped down
beforehand.
iii.Food or water are not allowed if a lab activity is ongoing
8 sep: start with quiz
• Life on earth is 3.8 billion years old.
– 1. write in years using scientific notation
a. 3.8x106yrs b. 3.8x109yr c. 3.8x1012yr d. 38x108yr
-- 2. write this in hours using scientific notation
– 3. if the average time from one generation to the
next is about one month, how many generations
have passed since life started?
• (you may not ignore sig figs for this problem)
The paradox of perception
• The size scope of physics is huge
• We see and experience a narrow slice
• Write the biggest thing, the smallest, the
fastest, the slowest
• (see human scale in physics)
Minilab 1
Work in groups of 2 (I assign)
One page with names, date, title, data, results
Hypothesis: We can estimate and measure the thickness
of a page and they will agree within 10%.
1. Estimate the thickness of a page in your text book.
2. Measure the thickness of a page using a micrometer
3. Compare these methods with two sentences
4. Answer the hypothesis
5. Dr. fisher to look at your classnotes during lab
End of chapter 1
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Numbers matter.
What you write communicates something
Don’t lie with numbers
Science is a process of learning
Physics is the science of matter and energy
Learn to use this text
Be safe in this lab
Review of minilab “reports”
• Any time you hand me the results of a lab, it
must communicate something.
• Can you read it and understand the point?
• In this case, did you answer the hypothesis?
• Did you show how you answered it?
• Even if your numbers are wrong, I will grade
you high if you communicate to me.
To be measured each time entering the lab for class
To be done in first minute (by one minute after the bell)
Take data and record (to maximum logical sig figs)
Make and maintain a graph of data vs. time (8 ½ x
11”)
Keep chart updated weekly, posted and neat
Purpose:
Handling data
Understanding and managing variability
Graphing for clarity
Analysis of the physics (later)
Raising interesting questions
Grade: yes
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Assignment
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Table A:
 Wt of fresh food item: apple, banana, carrot
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Table B
 Wt of cup of water covered and uncovered
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Table C
 Barometric pressure
 Humidity
 Room Temp
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Table D
 Outside temp
 24 hour min and max
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Table E
 Wt of fresh food item: apple, banana, carrot