Physics 201Professor P. Q. Hung

311B, Physics Building

Physics 201 – p. 1/21

Some Information

Class website:http://people.virginia.edu/∼xz5y/PHYS201/

All course information is on the aboveWebsite

Go to UVaCollab under Resources after everylecture to look at the notes.

Let’s go through some things

Physics 201 – p. 2/21

Some Information

Class website:http://people.virginia.edu/∼xz5y/PHYS201/

All course information is on the aboveWebsite

Go to UVaCollab under Resources after everylecture to look at the notes.

Let’s go through some things

Physics 201 – p. 2/21

Some Information

Class website:http://people.virginia.edu/∼xz5y/PHYS201/

All course information is on the aboveWebsite

Go to UVaCollab under Resources after everylecture to look at the notes.

Let’s go through some things

Physics 201 – p. 2/21

Some Information

Class website:http://people.virginia.edu/∼xz5y/PHYS201/

All course information is on the aboveWebsite

Go to UVaCollab under Resources after everylecture to look at the notes.

Let’s go through some things

Physics 201 – p. 2/21

What you need for the course

Textbook: Physics, 4th Edition by Walker, andMastering Physics

iClicker: Important to understand the policy(class website) for using this unit.

Physics 201 – p. 3/21

What you need for the course

Textbook: Physics, 4th Edition by Walker, andMastering Physics

iClicker: Important to understand the policy(class website) for using this unit.

Physics 201 – p. 3/21

Course Objectives:

To learn and understand the physical world

How? Problem Solving and ConceptualUnderstanding.

How to achieve that?LecturesReading and Conceptual quizzes in classHomeworksDiscussion Section Quizzes

Physics 201 – p. 4/21

Course Objectives:

To learn and understand the physical world

How? Problem Solving and ConceptualUnderstanding.

How to achieve that?LecturesReading and Conceptual quizzes in classHomeworksDiscussion Section Quizzes

Physics 201 – p. 4/21

Course Objectives:

To learn and understand the physical world

How? Problem Solving and ConceptualUnderstanding.

How to achieve that?LecturesReading and Conceptual quizzes in classHomeworksDiscussion Section Quizzes

Physics 201 – p. 4/21

Homework assignments

Homeworks will be found and submitted onMasteringPhysics. Register onMasteringPhysics now!

Check carefully the due date and time.

Look at the class homepage for policiesconcerning late homeworks.

Physics 201 – p. 5/21

Homework assignments

Homeworks will be found and submitted onMasteringPhysics. Register onMasteringPhysics now!

Check carefully the due date and time.

Look at the class homepage for policiesconcerning late homeworks.

Physics 201 – p. 5/21

Homework assignments

Homeworks will be found and submitted onMasteringPhysics. Register onMasteringPhysics now!

Check carefully the due date and time.

Look at the class homepage for policiesconcerning late homeworks.

Physics 201 – p. 5/21

Behavior to avoid in class

Surf the Web

Private chats

Entering and leaving class at inappropriatetimes

Loud snoring (with nightmares)

Physics 201 – p. 6/21

Behavior to avoid in class

Surf the Web

Private chats

Entering and leaving class at inappropriatetimes

Loud snoring (with nightmares)

Physics 201 – p. 6/21

Behavior to avoid in class

Surf the Web

Private chats

Entering and leaving class at inappropriatetimes

Loud snoring (with nightmares)

Physics 201 – p. 6/21

Behavior to avoid in class

Surf the Web

Private chats

Entering and leaving class at inappropriatetimes

Loud snoring (with nightmares)

Physics 201 – p. 6/21

How to learn from the Textbook

Work out the conceptual questions at the endof each chapter

Work out extra problems (call beyond duty)

Learn the strategy of problem solving fromProblem-Solving Summaries

Physics 201 – p. 7/21

How to learn from the Textbook

Work out the conceptual questions at the endof each chapter

Work out extra problems (call beyond duty)

Learn the strategy of problem solving fromProblem-Solving Summaries

Physics 201 – p. 7/21

How to learn from the Textbook

Work out the conceptual questions at the endof each chapter

Work out extra problems (call beyond duty)

Learn the strategy of problem solving fromProblem-Solving Summaries

Physics 201 – p. 7/21

Length, Mass and Time: SI units

Unit of length: meter (m)One ten-millionth of the distance betweenthe North Pole and the Equator, two markson a platinum-iridium rod in Paris.Distance traveled by light in vacuum in1/299,792,458 of a second.1 inch = 2.54 cm; 3.28 ft = 1 m

Physics 201 – p. 8/21

Length, Mass and Time: SI units

Unit of mass:kilogram (kg)Kilogram = mass of platinum-iridiumcylinder kept outside Paris.Mass (intrinsic property) 6= Weight (forcedue to gravity)

Physics 201 – p. 9/21

Length, Mass and Time: SI units

Unit of time: second (s)Earth rotation, etc...Most accurate: Atomic Clock (Cesium-133)

Physics 201 – p. 10/21

Length, Mass and Time: SI units

Typical distances

Physics 201 – p. 11/21

Length, Mass and Time: SI units

Typical masses

Physics 201 – p. 12/21

Length, Mass and Time: SI units

Typical times

Physics 201 – p. 13/21

Length, Mass and Time: SI units

Common prefixes

Keep your units straight!Physics 201 – p. 14/21

Dimensional Analysis

Apples 6= 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 ] ⇒ WrongDimension

Correct dependence: x = x0 + αvt. α: adimensionless constant determined byphysics.Let’s check: [L] = [L] + ([L]/[T])[T] Correct!

Physics 201 – p. 15/21

Dimensional Analysis

Apples 6= 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 ] ⇒ WrongDimension

Correct dependence: x = x0 + αvt. α: adimensionless constant determined byphysics.Let’s check: [L] = [L] + ([L]/[T])[T] Correct!

Physics 201 – p. 15/21

Significant Figures

Significant Figure = Number of digits knownwith certainty

Example: x = 2.5m ⇒ x is known to twosignificant figures.

Multiplication or Division: a × b = c or a/b = c⇒ number of sig fig for c = number of sig figof the least accurate of a or b. Same for morecomplicated expressions.

Addition or Subtraction: a + b = c or a − b = c⇒ number of decimal places for c = number ofdecimal places of the least accurate of a or b

Physics 201 – p. 16/21

Significant Figures

Significant Figure = Number of digits knownwith certainty

Example: x = 2.5m ⇒ x is known to twosignificant figures.

Multiplication or Division: a × b = c or a/b = c⇒ number of sig fig for c = number of sig figof the least accurate of a or b. Same for morecomplicated expressions.

Addition or Subtraction: a + b = c or a − b = c⇒ number of decimal places for c = number ofdecimal places of the least accurate of a or b

Physics 201 – p. 16/21

Significant Figures

Significant Figure = Number of digits knownwith certainty

Example: x = 2.5m ⇒ x is known to twosignificant figures.

Multiplication or Division: a × b = c or a/b = c⇒ number of sig fig for c = number of sig figof the least accurate of a or b. Same for morecomplicated expressions.

Addition or Subtraction: a + b = c or a − b = c⇒ number of decimal places for c = number ofdecimal places of the least accurate of a or b

Physics 201 – p. 16/21

Significant Figures

Significant Figure = Number of digits knownwith certainty

Example: x = 2.5m ⇒ x is known to twosignificant figures.

Multiplication or Division: a × b = c or a/b = c⇒ number of sig fig for c = number of sig figof the least accurate of a or b. Same for morecomplicated expressions.

Addition or Subtraction: a + b = c or a − b = c⇒ number of decimal places for c = number ofdecimal places of the least accurate of a or b

Physics 201 – p. 16/21

Example

The Coyote steadily sneaks upon theRoadrunner 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 = 6.48m2) 1.2m/s × 5.4s = 6.5m3) 1.2m/s × 5.35s = 6.42m ≈ 6.4m

(1): Incorrect number of Sig Fig in theanswer; Round-off error in the time

(2): Correct number of Sig Fig in the answerbut round-off error in the time

(3): Everything is done correctly

Physics 201 – p. 17/21

Example

The Coyote steadily sneaks upon theRoadrunner 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 = 6.48m2) 1.2m/s × 5.4s = 6.5m3) 1.2m/s × 5.35s = 6.42m ≈ 6.4m

(1): Incorrect number of Sig Fig in theanswer; Round-off error in the time

(2): Correct number of Sig Fig in the answerbut round-off error in the time

(3): Everything is done correctly

Physics 201 – p. 17/21

Example

The Coyote steadily sneaks upon theRoadrunner 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 = 6.48m2) 1.2m/s × 5.4s = 6.5m3) 1.2m/s × 5.35s = 6.42m ≈ 6.4m

(1): Incorrect number of Sig Fig in theanswer; Round-off error in the time

(2): Correct number of Sig Fig in the answerbut round-off error in the time

(3): Everything is done correctlyPhysics 201 – p. 17/21

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 knownto 2 sig figs.

Physics 201 – p. 18/21

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 knownto 2 sig figs.

Physics 201 – p. 18/21

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 knownto 2 sig figs.

Physics 201 – p. 18/21

Change of unit

Example: Kareem Abdul-Jabar is 7-foot-2. Howtall is he in meters?Answer: 1) 2 in = 1/6 ft; 2)7 − foot − 2 ≈ 7.16ft = 7.16ft/3.28ft = 2.18m.

Physics 201 – p. 19/21

Order-of-magnitude estimates

How many grains of rice are there in the jar lyingon that table in class?

Physics 201 – p. 20/21

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. 21/21

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. 21/21

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. 21/21

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. 21/21

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. 21/21

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. 21/21

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. 21/21

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. 21/21