Few Initial Remarks
Course: Phys-109
General Physics I
Text book: “Physics”, 6th edition, D. C. Giancoli.
Few Initial Remarks
Instructor: Dr. Mauricio Barbi
Email: [email protected]
Tel: 585-4260
Office: LB-212
Website:
http://ilc2.phys.uregina.ca/~barbi/academic/phys109/2010/phys109.html
Office Hours: Monday and Wednesday, 13:00-14:15h
Few Initial Remarks
My research interests:
I am physicist working in Experimental High Energy Particle
Physics (HEP).
1- Search for Dark Matter (connection between Particle
Physics and Cosmology with implications on the structure of
the universe)
2- Study of Neutrino Oscillation phenomena (recently
observed). Potential implication in several areas with
consequences that might include changes in some of the
current physics theories.
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Chapters to be covered:
1. Measurement; Estimating
2. Kinematics in One Dimension
3. Kinematics in Two Dimensions; Vectors
4. Dynamics (Newton’s Laws of Motion)
5. Circular Motion; Gravitation
6. Work and Energy
7. Linear Momentum
8. Rotational Motion
9. Static Equilibrium; Elasticity and Fracture
23. Light: Geometric Optics
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Class Grading
1.
2.
3.
4.
Weekly assignments: 20%
Midterm Exam: 15% (October 26)
Laboratory: 20%
Comprehensive Final Exam: 45% (December 14)
Notes:
i. If you fail the final, your grade will be given 100% of this
exam.
ii. If, for any well justified reason, you miss the midterm exam,
the final exam will account for 60% of your grade.
iii.An equation sheet and a list with fundamental constants will
be provided for the exams. No other aids will be allowed
such as calculators, electronic translators, cell phones,
ipods, laptops, etc, without permission.
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Assignments: Assignments have to be handed in
at the beginning of the class on the due date
indicated on the class website. Late assignments
will be tolerated if handed in no later than the
beginning of the next class following the original
due date with a cumulative 10% a day penalty to
the assignment.
Solutions of problems have to be given in full
and written clearly, showing all your work and
detailing your calculations in an organized way.
Ineligible solutions will not be considered.
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Important: University picture ID is required to write
exams
Special Needs: Feel free to contact me early in the
semester to discuss issues regarding any special
needs. You should also contact the Coordinator of
Special Needs Services at 585-4631.
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Tutorials: A Tutorial session has been scheduled for
every (TBA) until the end of the semester.
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Supplemental Instruction (SI): The Faculty Of
Sciences offers supplemental instructions every
Monday – 9:30-10:30h
Tuesday – 11:30-12:30h
Wednesday – 15:30-16:30h
in LB-205.
Your SI instructor is Stephanie.
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Last, but not least!
I encourage students to ask questions in
class. Discussions other than
physics will not be tolerated.
You can also come to my office during
my “office hours” for any physicsrelated discussion.
Chapter 1
Introduction, Measurement,
Estimating
Units of Chapter 1
1. The Nature of Science
2. Physics and Its Relation to Other Fields
3. Models, Theories, and Laws
4. Measurement and Uncertainty; Significant
Figures
5. Units, Standards, and the SI System
6. Converting Units
7. Order of Magnitude: Rapid Estimating
8. Dimensions and Dimensional Analysis
The Nature of Science
 Observation: important first step toward scientific
theory; requires imagination to tell what is important.
 Theories: create to explain observations; will make
predictions.
 Observations will tell if the prediction is accurate, and
the cycle goes on.
Models are also very useful during the process of
understanding phenomena. It is mostly based on
observation and some assumptions that are not
necessarily accurate.
The Nature of Science
How does a new theory get accepted?
• Predictions agree better with data
• Explains a greater range of phenomena
Ptolemy’s geocentric view
of the universe
Copernicus’s heliocentric view
of the universe
Physics and Its Relation to Other Fields
Physics is needed in both architecture and engineering. Other fields
also use physics, and make contributions to it: physiology, zoology, life
sciences, etc.
Communication between architects and engineers is essential if
disasters are to be avoided.
Measurement and Uncertainty; Significant
Figures
No measurement is exact; there is always
some uncertainty due to limited instrument
accuracy and difficulty reading results.
The photograph to the left
illustrates this – it would
be difficult to measure the
width of this 2x4 to better
than a millimeter.
Measurement and Uncertainty; Significant
Figures
Estimated uncertainty is written with a ± sign; for
example:
Percent uncertainty is the ratio of the uncertainty
to the measured value, multiplied by 100:
Measurement and Uncertainty; Significant
Figures
The number of significant figures is the number of reliably
known digits in a number. It is usually possible to tell the number
of significant figures by the way the number is written:
• Non-zero digits are always significant; 23.21 cm has 4 significant
figures
Measurement and Uncertainty; Significant
Figures
• When are zeroes significant?
a) Zeroes placed before other digits are not significant; 0.046 has two
significant figures.
b) Zeroes placed between other digits are always significant; 4009 has
four significant figures.
c) Zeroes placed after other digits but behind a decimal point are
significant; 7.90 has three significant figures.
d) Zeroes at the end of a number are significant only if they are behind a
decimal point as in (c); 7.0 has two significant figures.
e) Ambiguity: You can say that the number 8200 has two significant
figures, but it could also be three or four. To avoid uncertainty, use
scientific notation to place significant zeroes behind a decimal point:
8.200 x 103 has four significant digits
8.20 x 103 has three significant digits
8.2 x 103 has two significant digits
Measurement and Uncertainty; Significant
Figures
In calculations involving multiplication, division, trigonometric functions, etc,
the result has as many significant figures as the number used in the
calculation with the fewest significant figures.
Example: 11.3 cm x 6.8 cm = 77 cm (two significant figures) and not 76.84.
Problem: How many significant figures do you expect in the following
calculation: sin(0.097 x 4.73)?
Answer: two significant figures.
When adding or subtracting, the number of decimal places (not significant
figures) in the answer should be the same as the least number of decimal
places in any of the numbers being added or subtracted, or in other words no
more accurate than the least accurate number used.
Example: 6.1 Kg + 5.97 Kg + 1.4501 Kg = 13.5 Kg (and not 13.5201)
Measurement and Uncertainty; Significant
Figures
Note:
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.
Remark: When doing multi-step calculations, keep at
least one more significant digit in intermediate results
than needed in your final answer
Units, Standards, and the SI System
We will be working in the SI system, where the
basic units are meters, kilograms, and seconds
(MKS).
Other systems: cgs; units are
centimeters, grams, and seconds.
British engineering system has force
instead of mass as one of its basic
quantities, which are feet, pounds, and
seconds.
Units, Standards, and the SI System
Quantity Unit
Standard
Length
Meter
Length of the path traveled by light
in 1/299,792,458 second.
Time
Second
Time required for 9,192,631,770
periods of radiation emitted by
cesium atoms
Mass
Kilogram
Platinum cylinder in International
Bureau of Weights and Measures,
Paris
Units, Standards, and the SI
System
These are the standard SI prefixes for
indicating powers of 10.
Many are familiar; milli, mega, etc.
Y, Z, E, h, da, a, z, and y are rarely
used.
Dimensions and Dimensional Analysis
Dimensions of a quantity are the base units that make it up; they are
generally written using square brackets.
Example: Speed = distance / time
Dimensions of speed: [L/T]
Quantities that are being added or subtracted must have the same
dimensions. In addition, a quantity calculated as the solution to a
problem should have the correct dimensions.
Important remarks:
- Make sure you always “carry” units in your calculations;
4 m + 4 m = 8 m (instead of 4 +4 = 8 m).
-Always check to see if the units are correct in your results.
5 m/s x 2 s = 10 m
Summary of Chapter 1
• Theories are created to explain observations,
and then tested based on their predictions.
• A model is like an analogy; it is not intended to
be a true picture, but just to provide a familiar
way of envisioning a quantity.
• A theory is much more well-developed, and can
make testable predictions; a law is a theory that
can be explained simply, and which is widely
applicable.
• Dimensional analysis is useful for checking
calculations.
Summary of Chapter 1
• Measurements can never be exact; there is
always some uncertainty. It is important to
write them, as well as other quantities, with the
correct number of significant figures.
• The most common system of units in the
world is the SI system.
• When converting units, check dimensions to
see that the conversion has been done
properly.
• Order-of-magnitude estimates can be very
helpful.