College Physics
（大学物理）
Qingxu Li (李清旭)
Tel: 62471347, Email: liqx@cqupt.edu.cn
Room 306, College of Mathematics and Physics
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“The most incomprehensible thing about the
universe is that it is comprehensible.”
— Albert Einstein
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College Physics
• Textbook
Physics for Scientists and Engineers with Modern Physics (3rd
Ed.), by D. C. Giancoli; 滕小瑛改编, 高等教育出版社
• Reference Books
Feynman’ Lectures on Physics, by R. P. Feynman
物理学, 第五版, 马文蔚改编, 高等教育出版社
• Grades
Final Exam (70%) + Performance (30%)
• Notes
a. Exercises and Exam are to be finished in English
b. Useful materials can be found in the site slxy.cqupt.edu.cn
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Contents to be Discussed
• Classical /Newtonian Mechanics (28
Periods)
• Wave/Physical Optics (20 Periods)
• Electromagnetism
• Introduction to Modern Physics
Relativity, Quantum Physics, etc.
(Chp. 15-18, 23-24, 36-40 will not be discussed
in the course)
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The Nature of Sciences (Physics)
Observations  Experiments
Explanations  Theories
Verifications  Testing
Up to date: A theory cannot be
absolutely verified!
Three ways to unknown: Expt., Theor., Comput.
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Models and Theories
（模型和理论）
Model
A model is an analogy or mental image of the phenomena
in terms of something we are familiar with. A model gives
us an approximate mental or visual image for what actually
is happening. In simple, a model is a simplified substitute
for the real problem that allow us to solve the problem in
a relatively simple way.
A theory is broader and more detailed than a model, and
it attempts to solve a set of problems with great precision.
Models often lead to important theories. It is important to
tell the differences between the models or theories and the
real systems or the phenomena themselves.
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Physical Laws
（物理定律）
Laws or physical laws are concise but general
statements about how nature behaves, and sometimes the statement takes the form of a relationship
or equation between quantities.
Scientific laws are descriptive: they do NOT say
How nature should behave, but rather are meant to
describe how nature does behave. Laws are also
can not be tested in the infinite variety of cases.
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Measurement and Uncertainty
（测量及其误差）
Experiments and therefore measurements play an
essential role in physics.
Accurate measurement are undoubtedly important,
but no measurement is absolutely precise. There is
always an uncertainty associated with every measure
-ment.
(accuracy and precision, P3)
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Significant Figures
（有效数字）
In general, a significant figure in a measurement is a reliably
known digit. You SHOULD avoid the temptation to keep more
digits in the final answer than is justified.
When multiplying several quantities, the number of significant
figures in the final answer is the same as the number of significant
figures in the quantity having the lowest number of significant
figures. The same rule applies to division.
When numbers are added or subtracted, the number of decimal
places in the result should equal to the smallest number of decimal
places of any term in the sum.
the number of decimal places 小数点后的位数
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However, to obtain the most accurate result, you should
normally keep an extra significant figure or two throughout a
calculation, and round off only in the final result.
General rule for rounding off numbers: the last digit retained is
to be increased by 1 if the last digit dropped is greater than 5. If
the last digit dropped is less than 5, the last digit retained remains
unchanged. If the last digit dropped is equal to 5, the remaining
digit should be rounded to the nearest even number.
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Scientific Notion
Numbers are commonly written in “powers of ten”,
or “scientific notion”.
0.0030  3.0 103 , 34500=3.45 104
One advantage of scientific notion is that it allows the
number of significant figures to be clearly expressed.
E.g., 36900 can be expressed as 3.69 104 or 3.690 104 ,
but the latter has one more significant figure.
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Standards of Length, Mass, and Time
(SI system, Système International)
Length, meter （长度，米）
The meter: the distance traveled by light in a vacuum during
a time of 1/299792458 second.
Mass, kilogram （质量，千克）
The kilogram: the mass of a specific platinum-iridium alloy
cylinder kept at the International Bureau of Weights and
Measures at Sevres, France.
Time, second （时间，秒）
The second: 9192631770 times the period of oscillation of
radiation from the cesium atom.
(P5, Table 1-1, 1-2, 1-3, 1-4, 1-5)
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Estimates and Order-of-Magnitude Calculations
（估算和数量级计算）
Order-of-Magnitude is valuable when little information
is available and an approximate answer is useful.
order-of-magnitude
a certain quantity as the power of ten of the number that
describe that quantity
For an order-of-magnitude calculation, the results are
reliable to within about a factor of 10.
Example 1-4, 1-5.
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Dimensional Analysis
（量纲分析）
Dimension denotes the physical nature of a quantity
Dimensions of length, mass, and time: L, M, and T.
Dimensions can be treated as algebraic quantities
Quantities can be added or subtracted only if they have the
same dimensions.
An arbitrary equation holds, if and only if the dimensions
on the two sides of the equation.
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Principles of Physics, Serway and Jewett.
P44 3-1---3-5
Vector （矢量）
A vector is specified by both magnitude and direction.
For an arbitrary vector A
A   Ax , Ay , Az   AeA ; A  Ax2  Ay2  Az2
A is called the  -component of A.

A is called the magnitude of A. sometimes called module, A  A

A
Unit vector of vector A: eA    cos  , cos  , cos  
A
magnitude 大小，数量，震级
module 模
direction 方向
unit vector 单位矢量
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Properties of Vector
equality A  B  A  B ;


  x, y, z
addition C  A  B  C  A  B



subtraction C  A  B  C  A  B



multiplication of a vector by a scalar
C   A  C  A
addition: the triangle method of addition or parallelogram rule of addition
（矢量求和：三角形法则或者平行四边形法则）
equality 相等，addition 加法，subtraction 减法，multiplication 乘法
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dot product/inner product/scalar product:
A  B  a scalar  Ax Bx  Ay By  Az Bz
cross product/vector product:
A  B  a vector
 A B
 A B
 A B
z
x
y
 Ax By  Ay Bx
 Ay Bz  Az By
 Az Bx  Ax Bz
 AB
Notes :
A  B  AB cos  AB ,
A  B  AB sin  AB .
Here  AB is the angle between vector A and vector B.
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Scalar Vs Vector
（矢量和标量）
path Vs displacement vector
As a particle moves from A to B along an arbitrary path
represented by the broken line, its displacement is a vector quantity
shown by the arrow draw from A to B.
Fig. 1.1
path 路程
displacement 位移
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Problems
P13: 8, 23, 38
P69: 12,15
This PPT file can be downloaded from the website:
slxy.cqupt.edu.cn
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