Physics 140 – Winter 2015
Prof. Keith Riles
January 7
LIGO Hanford
Observatory
(Washington)
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Physics 140 is a calculus-based introductory course intended for
• engineering students
• potential majors in the natural sciences
• students skilled in trigonometry, algebra & calculus
Physics 140 is generally not intended for
• pre-medical / nursing students (see physics 135)
• students looking only to satisfy Nat Sci distribution
• students with no background in calculus
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Overarching goals for this course:
1.
Gain solid grounding in Newtonian mechanics
2. Gain reliable intuition
3.
Learn to solve hard problems
1. Analytically
2. Via numerical modeling (programming)
This course is largely devoted to understanding motion:
• Kinematics – Description of motion
• Dynamics – Causes of (and constraints on) motion
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We will study the motion of various objects:
• Idealized particles
• Rigid bodies, including their rotation
• Flexible, elastic bodies, e.g., waves on strings
• Systems of particles, including fluids
We will study both translational
dynamics and the rotational analog
(which follows from the first) 5
Four Fundamental Forces of Nature
Force
Relative
Strength
Distance Scale
Manifestation
Strong
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~10-15 m
Holds nuclei
together
Electromagnetic
~10-2
Infinity
Holds atoms
(+people)
together
Weak
~10-13
~10-18 m
Certain
radioactivity
Gravitational
~10-43
Infinity
Holds Earth /
Galaxy together
Two force types we encounter every day
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Gravity is obvious
Electromagnetic force may seem
surprising to you, but it helps to
realize that the dominant force
between atoms is electromagnetic
Pushing an object is fundamentally
an electromagnetic act
Gravity is intrinsically weaker at the
microscopic level, but the mass of the
entire Earth makes the total force
large
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Examples of Forces
Gravitational:
Force between masses M and m separated by distance r
Mm
F=G 2
r
Force on mass m near Earth’s surface
F = mg
Electromagnetic:
Restoring spring force
F = -kx
Normal force (special case of restoring force)
Friction – dissipative (mechanical energy lost)
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We will study Newtonian
Mechanics which works very well
in most cases
But it breaks down in these regimes:
• at very small (atomic) distances (quantum mechanics)
• at very high speeds (special relativity)
• under strong gravity (general relativity)
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Physics is both:
A fundamental science to understand & explain
the laws that govern the natural world
and…
A set of tools to apply in other science and
engineering
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Fundamental Science
The M81 galaxy spins too fast for its stars alone to hold it together
About 4/5 of all matter is “Dark”
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Fundamental Science
Large Hadron Collider (Switzerland)
The LHC
accelerator at
CERN may allow
creation and
discovery of the
elementary
particles that make
up Dark Matter
(now that the
elusive Higgs
Boson has been
nabbed)
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Fundamental Science
Tracking the orbits of
stars near our galaxy’s
center (Sagittarius A)
reveals the presence of a
different kind of dark
matter – a supermassive
Black Hole heavier than
3.7 million Suns!
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Fundamental Science
The spiraling collisions of smaller
black holes and neutron stars should
create (according to Einstein) ripples
in space itself, known as
Gravitational Waves.
LIGO Hanford
Observatory
(Washington)
I collaborate with other
physicists on an experiment
called LIGO to search for
those waves with giant laser
interferometers.
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Physics as a Tool – Medicine
Ultrasound Imaging
And of
course,
X-rays
…
Magnetic Resonance Imaging
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Physics as a Tool – Technology
Solar
Energy
Data
Storage
Laser Fusion
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Physics as a Tool – Civil Engineering
Hoover Dam (1936) and its Bypass Bridge (2010)
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Physics as a Tool – Engineering
Temporary suspension bridge
Closing the gap
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Physics as a Tool – Engineering
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Physics as a Tool – Avoiding Mistakes
Tacoma Narrows Bridge – 1940
Gare Montparnasse – 1896
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Course logistics
• Course web site: http://ctools.umich.edu
• Textbook: Young & Freedman (13th ed)
• Reading assignments – see CTools syllabus
• Viewing – see CTools schedule page for youtube links
• Slides shown in class placed in Ctools resources
• Class participation via i>clickers
• On-line homework via Mastering Physics (MaPhys)
• Numerical modeling homework –using Python/VPython
• Grade reports via Gradebook 2 system (see CTools link)
• Exams: 3 midterms (1.5 hr) and one final (2 hr)
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What about grades?
You will receive an overall score S, derived from weighting the
course elements (on a 0-100 scale) as follows:
S = 0.20 (Mastering Physics homework)
+ 0.10 (participation - iclicker)
+ 0.14 (numerical modeling homework)
+ 0.12 (exam 1) + 0.12 (exam 2) + 0.12 (exam 3)
+ 0.20 (final)
Letter grade determination:
Based on your overall score
A (85), B (75-85), C (60-75), D (45-60), E (<45)
Extra credit opportunities on some numerical modeling homeworks
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What you should do for Physics 140 now
• Read the contents of the PHYSICS 140 CTools site
http://ctools.umich.edu
• Sign up for a MaPhys account, begin first assignment
• Read Chapter 1 of Y&F
• Purchase and register i>clicker remote
• Download & install Python/Vpython on your laptop
(see instructions on the CTools site)
• Consider joining an SLC study group
• Registration opens Friday January 16 at noon.
• First group meetings on Sunday January 18
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How can I do well in this course?
Be observant
Think about physics - it’s all around you!
Be organized
Allocate time (10%?) for reading/ homework/ study group
Be active
Try several approaches to studying & problem solving,
work with your peers (e.g., SLC-led study group)
Join the Piazza discussion groups (on Ctools)
Be patient
If at first you don’t succeed…
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Class sessions
• Except for today, classes will not be traditional lectures
• Mini-lectures will be posted on youtube in advance of class
• I will assume you have viewed those lectures
• I will focus in class on problem solving via peer instruction and
on demonstrations to illustrate concepts
• Feel free to e-mail me (kriles@umich.edu) questions you may
have after viewing videos
Recent academic research (confirmed in U-M physics courses in
recent years) has shown that active learning via working in groups
to solve posed problems leads to deeper understanding – as
measured via exam performance.
To ensure that you benefit from this instruction, you will be asked
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to answer questions in class via i>clickers…
Normally:
• Right answer: 4 points
• Wrong answer: 3 points*
• No answer:
0 points
But everyone excused this week!
Let’s try an i>clicker question!
Where are you from?
A.
B.
C.
D.
E.
Ann Arbor
Michigan palm
Michigan U.P.
USA (outside MI)
Outside USA
*No points for incorrect answers
to pre-lecture video questions
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Another one:
You plan to pursue a career in...
A) Engineering
B) Physics or physical sciences (astronomy, geophysics,
biophysics, etc)
C) Other natural sciences (chemistry, biology, etc)
D) Mathematics or computer science
E) Non-science
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And one more…
You are buying a tennis racket with tennis balls. The
sales person tells you that together they cost $110,
and that the racket costs $100 more than the balls.
How much do the tennis balls cost?
A. $110
B. $100
C. $10
D. $5
E. $0
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Numerical modeling homework & labs
Numerical modeling (and programming) have become essential skills to many
engineers and scientists
Numerical modeling goals for this course:
• Solve realistic problems without relying on poor analytical approximations
• Learn basic algorithms for modeling and assessing accuracy
• Learn systematic comparison of analytical and numerical methods
• Learn rudiments of computer programming (Python & Vpython)
Example:
• Tiger Woods can hit a golf ball hundreds of yards
• According to standard textbook approximations, he can hit much farther
• You will show the difference!
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Numerical modeling homework & labs
Every Thursday we will meet in Angell Hall Auditorium D. Starting next week will
be numerical modeling labs devoted to getting you started on the modeling
homework due (usually) the following week (extensions given during exam weeks).
There will be ten computer labs during the semester to which you should bring a
laptop pre-loaded with the Python and Vpython programming language packages
(see Ctools sidebar for installation information).
Some assignments later in the semester will offer extra credit opportunity.
Please start the Vpython tutorials (CTools) before next week’s lab!
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Syllabus on Ctools
(partial snapshot)
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Progression of course
Vectors
1-D motion
2-D & 3-D motion
Circular & relative motion
Newton’s Laws
Tomorrow’s material
 Exam 1 on February 5 (chapters 1-5)
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Progression of course
Work and kinetic energy
Potential energy
Momentum & impulse
Collisions & center of mass
Rotational kinematics
Rotational dynamics
 Exam 2 on March 12 (chapters 6.1-10.2)
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Progression of course
Angular momentum
Equilibrium
Fluid statics
Fluid dynamics
Gravitation
Exam 3 on April 9 (chapters 10.3-13.7)
Oscillations
Mechanical waves
 Final exam on April 24 (chapters 1-15)
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This course is challenging!
But it’s also important
Foundational course for your career
Treat it as a serious investment with
great future dividends
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Questions?
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