Physics 201
Professor P. Q. Hung
311B, Physics Building
Physics 201 – p. 1/2
Some Information
Class website:
http://people.virginia.edu/∼xz5y/PHYS201/
Physics 201 – p. 2/2
Some Information
Class website:
http://people.virginia.edu/∼xz5y/PHYS201/
All course information is on the above
Website
Physics 201 – p. 2/2
Some Information
Class website:
http://people.virginia.edu/∼xz5y/PHYS201/
All course information is on the above
Website
Go to UVaCollab under Resources after every
lecture to look at the notes.
Physics 201 – p. 2/2
Some Information
Class website:
http://people.virginia.edu/∼xz5y/PHYS201/
All course information is on the above
Website
Go to UVaCollab under Resources after every
lecture to look at the notes.
Let’s go through some things
Physics 201 – p. 2/2
What you need for the course
Textbook: Physics, 4th Edition by Walker, and
Mastering Physics
Physics 201 – p. 3/2
What you need for the course
Textbook: Physics, 4th Edition by Walker, and
Mastering Physics
iClicker: Important to understand the policy
(class website) for using this unit.
Physics 201 – p. 3/2
Course Objectives:
To learn and understand the physical world
Physics 201 – p. 4/2
Course Objectives:
To learn and understand the physical world
How? Problem Solving and Conceptual
Understanding.
Physics 201 – p. 4/2
Course Objectives:
To learn and understand the physical world
How? Problem Solving and Conceptual
Understanding.
How to achieve that?
Lectures
Reading and Conceptual quizzes in class
Homeworks
Discussion Section Quizzes
Physics 201 – p. 4/2
Homework assignments
Homeworks will be found and submitted on
MasteringPhysics. Register on
MasteringPhysics now!
Physics 201 – p. 5/2
Homework assignments
Homeworks will be found and submitted on
MasteringPhysics. Register on
MasteringPhysics now!
Check carefully the due date and time.
Physics 201 – p. 5/2
Homework assignments
Homeworks will be found and submitted on
MasteringPhysics. Register on
MasteringPhysics now!
Check carefully the due date and time.
Look at the class homepage for policies
concerning late homeworks.
Physics 201 – p. 5/2
Behavior to avoid in class
Surf the Web
Physics 201 – p. 6/2
Behavior to avoid in class
Surf the Web
Private chats
Physics 201 – p. 6/2
Behavior to avoid in class
Surf the Web
Private chats
Entering and leaving class at inappropriate
times
Physics 201 – p. 6/2
Behavior to avoid in class
Surf the Web
Private chats
Entering and leaving class at inappropriate
times
Loud snoring (with nightmares)
Physics 201 – p. 6/2
How to learn from the Textbook
Work out the conceptual questions at the end
of each chapter
Physics 201 – p. 7/2
How to learn from the Textbook
Work out the conceptual questions at the end
of each chapter
Work out extra problems (call beyond duty)
Physics 201 – p. 7/2
How to learn from the Textbook
Work out the conceptual questions at the end
of each chapter
Work out extra problems (call beyond duty)
Learn the strategy of problem solving from
Problem-Solving Summaries
Physics 201 – p. 7/2
Length, Mass and Time: SI units
Unit of length: meter (m)
One ten-millionth of the distance between
the North Pole and the Equator, two marks
on a platinum-iridium rod in Paris.
Distance traveled by light in vacuum in
1/299,792,458 of a second.
1 inch = 2.54 cm; 3.28 ft = 1 m
Physics 201 – p. 8/2
Length, Mass and Time: SI units
Unit of mass:kilogram (kg)
Kilogram = mass of platinum-iridium
cylinder kept outside Paris.
Mass (intrinsic property)6= Weight (force
due to gravity)
Physics 201 – p. 9/2
Length, Mass and Time: SI units
Unit of time: second (s)
Earth rotation, etc...
Most accurate: Atomic Clock (Cesium-133)
Physics 201 – p. 10/2
Length, Mass and Time: SI units
Typical distances
Physics 201 – p. 11/2
Length, Mass and Time: SI units
Typical masses
Physics 201 – p. 12/2
Length, Mass and Time: SI units
Typical times
Physics 201 – p. 13/2
Length, Mass and Time: SI units
Common prefixes
Keep your units straight!
Physics 201 – p. 14/2
Dimensional Analysis
Apples6= Oranges
Position versus time: Is x = x0 + vt2 correct?
x: distance [L]
v: velocity (distance/time) [L]/[T]
vt2 : ([L]/[T ]) × [T ]2 = [L] × [T ] ⇒ Wrong
Dimension
Physics 201 – p. 15/2
Dimensional Analysis
Apples6= Oranges
Position versus time: Is x = x0 + vt2 correct?
x: distance [L]
v: velocity (distance/time) [L]/[T]
vt2 : ([L]/[T ]) × [T ]2 = [L] × [T ] ⇒ Wrong
Dimension
Correct dependence: x = x0 + αvt. α: a
dimensionless constant determined by
physics.
Let’s check: [L] = [L] + ([L]/[T])[T] Correct!
Physics 201 – p. 15/2
Significant Figures
Significant Figure = Number of digits known
with certainty
Physics 201 – p. 16/2
Significant Figures
Significant Figure = Number of digits known
with certainty
Example: x = 2.5m ⇒ x is known to two
significant figures.
Physics 201 – p. 16/2
Significant Figures
Significant Figure = Number of digits known
with certainty
Example: x = 2.5m ⇒ x is known to two
significant figures.
Multiplication or Division: a × b = c or a/b = c
⇒ number of sig fig for c = number of sig fig
of the least accurate of a or b. Same for more
complicated expressions.
Physics 201 – p. 16/2
Significant Figures
Significant Figure = Number of digits known
with certainty
Example: x = 2.5m ⇒ x is known to two
significant figures.
Multiplication or Division: a × b = c or a/b = c
⇒ number of sig fig for c = number of sig fig
of the least accurate of a or b. Same for more
complicated expressions.
Addition or Subtraction: a + b = c or a − b = c
⇒ number of decimal places for c = number of
decimal places of the least accurate of a or b
Physics 201 – p. 16/2
Example
The Coyote steadily sneaks upon the
Roadrunner with a constant speed of 1.2 m/s.
How much distance has he covered after 5.35 s?
1) 1.2m/s × 5.4s = 6.48m
2) 1.2m/s × 5.4s = 6.5m
3) 1.2m/s × 5.35s = 6.42m ≈ 6.4m
(1): Incorrect number of Sig Fig in the
answer; Round-off error in the time
Physics 201 – p. 17/2
Example
The Coyote steadily sneaks upon the
Roadrunner with a constant speed of 1.2 m/s.
How much distance has he covered after 5.35 s?
1) 1.2m/s × 5.4s = 6.48m
2) 1.2m/s × 5.4s = 6.5m
3) 1.2m/s × 5.35s = 6.42m ≈ 6.4m
(1): Incorrect number of Sig Fig in the
answer; Round-off error in the time
(2): Correct number of Sig Fig in the answer
but round-off error in the time
Physics 201 – p. 17/2
Example
The Coyote steadily sneaks upon the
Roadrunner with a constant speed of 1.2 m/s.
How much distance has he covered after 5.35 s?
1) 1.2m/s × 5.4s = 6.48m
2) 1.2m/s × 5.4s = 6.5m
3) 1.2m/s × 5.35s = 6.42m ≈ 6.4m
(1): Incorrect number of Sig Fig in the
answer; Round-off error in the time
(2): Correct number of Sig Fig in the answer
but round-off error in the time
(3): Everything is done correctly
Physics 201 – p. 17/2
Scientific Notation
Example: Speed of Light = 299, 792, 458 m/s.
Known to 9 sig figs.
Physics 201 – p. 18/2
Scientific Notation
Example: Speed of Light = 299, 792, 458 m/s.
Known to 9 sig figs.
It can be written as 2.99792458 × 108 m/s.
Physics 201 – p. 18/2
Scientific Notation
Example: Speed of Light = 299, 792, 458 m/s.
Known to 9 sig figs.
It can be written as 2.99792458 × 108 m/s.
One can write it as 3.0 × 108 m/s if it is known
to 2 sig figs.
Physics 201 – p. 18/2
Change of unit
Example: Kareem Abdul-Jabar is 7-foot-2. How
tall is he in meters?
Answer: 1) 2 in = 1/6 ft; 2)
7 − f oot − 2 ≈ 7.16f t = 7.16f t/3.28f t = 2.18m.
Physics 201 – p. 19/2
Order-of-magnitude estimates
How many grains of rice are there in the jar lying
on that table in class?
Physics 201 – p. 20/2
Problem Solving
Read the problem carefully
Physics 201 – p. 21/2
Problem Solving
Read the problem carefully
Sketch the system
Physics 201 – p. 21/2
Problem Solving
Read the problem carefully
Sketch the system
Visualize the physical process
Physics 201 – p. 21/2
Problem Solving
Read the problem carefully
Sketch the system
Visualize the physical process
Find a strategy
Physics 201 – p. 21/2
Problem Solving
Read the problem carefully
Sketch the system
Visualize the physical process
Find a strategy
Find the appropriate equations
Physics 201 – p. 21/2
Problem Solving
Read the problem carefully
Sketch the system
Visualize the physical process
Find a strategy
Find the appropriate equations
Solve the equations
Physics 201 – p. 21/2
Problem Solving
Read the problem carefully
Sketch the system
Visualize the physical process
Find a strategy
Find the appropriate equations
Solve the equations
Check your answer
Physics 201 – p. 21/2
Problem Solving
Read the problem carefully
Sketch the system
Visualize the physical process
Find a strategy
Find the appropriate equations
Solve the equations
Check your answer
Limits and special cases
Physics 201 – p. 21/2