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Department of Physics and Applied Physics 95.141, Fall 2013, Lecture 1

CHOWDHURY 95.141 PHYSICS I SPRING 2013 LECTURE 1

95.141

Welcome to Physics I Andriy Danylov

http://faculty.uml.edu/Andriy_Danylov/Teaching/PhysicsI/

Course Website

http://echo360.uml.edu/danylov2013/physics1fall.html

Lecture (video)

http://faculty.uml.edu/Andriy_Danylov/Teaching/PhysicsI

http://faculty.uml.edu/pchowdhury/95.141/

../../MOVIES/Physics 1 video example problems/Trailer for Class.mov



Today’s Agenda

Course details

Website

Organization

Textbook

Homework

Mastering Physics

Grading

Tutoring

Exams

Chapter 1

Measurement

Uncertainty

Significant figures

Units

Conversions

Estimations


Clickers

You need to register your clicker online at

http://www1.iclicker.com/register-an-iclicker using the code

found on the back of the clicker, and your university ID number.

You must return your clicker at the end of the semester

http://www1.iclicker.com/register-an-iclicker






Clickers

• You can answer questions posed by the

lecturer with a clicker

• You must have your own clicker!! o You cannot borrow a friend’s clicker for class

o You may not have more than 1 clicker in class: this is academic

fraud.

• Clickers will be used to determine class

participation

• Clickers will be used from next week!!


Course Website

Everything you need to know about the course can be found on the course website:

http://faculty.uml.edu/Andriy_Danylov/Teaching/PhysicsI/

http://faculty.uml.edu/Andriy_Danylov/Teaching/PhysicsI

http://faculty.uml.edu/pchowdhury/95.141/


Course Organization

Physics I meets 4 times a week

• Lectures : 9:00-9:50 MW, Olney 150

• Recitation Sections

Various times (M/W or Tu/Fr) and locations

RECITATIONS MEET THIS WEEK Wed and Fri !

LABS MEET NEXT WEEK!

Text: Giancoli: Physics for Scientists and Engineers, 4th Ed.


• New topics ahead of recitations

• Clicker questions

• Example problems

• Movie clips

• Demonstrations

Lecture slides will be posted on-line

Lecture recording (video and audio) will be posted:

Lectures




Recitations • Lecture review (5-10 min)

• Example problems from

the textbook

• Quizzes

(weekly, 10 min)

• Written HW

(collected and graded)


Weekly Homework

• ALL HW is on www.masteringphysics.com

Course: “95141Fall2013”

Course ID: MPDANYLOV44541

• The online HW is typically due on Sunday at 6 pm.

(You are penalized 25% for each day late)

• Weekly HWs count for 100 points/750

(80 online, 20 written).

• Recitation instructors will collect written homework weekly.

• Homework assignments are available at course website

http://www.masteringphysics.com/


www.masteringphysics.com

http://www.masteringphysics.com


Recitation Quizzes Given by recitation instructor, during recitation.

100/750 of Final Grade.

Typically covers material from previous week’s

class/recitation and homework.


MATH DIAGNOSTIC QUIZ

• Given in your first recitation.

• This is a check of very basic math skills.

• Meant to be a diagnostic tool for you & us.

• See where your quantitative skills stand.

• See if you are prepared for this very challenging

course.

10 points for all for just taking it.


Physics I Resources

• Get help early and often.

• The first person to contact with problems in Physics I is your Recitation Instructor!!

• Recitation Instructors will have office hours each week during which they can be met.

• Physics Department Tutoring Center: Tutors are available free of charge in the Physics Department tutoring room (9 am-5 pm), located adjacent to the Department office on the 1st floor of Olney Hall.


EXAMS

3 Mid-Term (in-class) Exams

Each worth 100 pts.

Covers incremental material from previous exam

No rescheduling

(Extra time available for students with note from Student Disability Services)

Final Exam 200 pts (in-class) .

Date/Time/Location To Be Announced


Course Grading

Item Points

Class Participation 40

Weekly HW 100

Quizzes 100

Math Quiz 10

Exam 1 100

Exam 2 100

Exam 3 100

Final Exam 200

Total 750

Range Grade

>80% A

75-80% A-

70-75% B+

65-70% B

60-65% B-

55-60% C+

50-55% C

45-50% C-

40-45% D+

35-40% D

<35% F


Introductory Physics

//localhost/Users/Partha1/Documents/My Documents/Teaching/95.141/Wasserman-Fall10/Lectures/movies/Trailer for Class.mov


Measurement and uncertainty

There are 3 parts to a measurement:

1)The measurement (13.2)

2)The unit (g)

3)The uncertainty (±0.4)

(No measurement should be written without all three parts)

NO measuring device can give perfect measurements

without experimental uncertainty.

Convention: If uncertainty is not mentioned,

13.2 g is said to have an uncertainty of ±0.1 g (Which means we are reasonably sure the actual weight is somewhere

between 13.1 and 13.3)

13.20 g

13.200 g (uncertainty ±0.01g) (uncertainty ±0.001g)


Percentage uncertainty

SO, the uncertainty in the measurement can be provided

• either in absolute numbers: e.g. 0.1g

• or as a percentage: 13.2g +/- 0.7%

The percent uncertainty is the ratio of the uncertainty to the measured value, multiplied by 100


Significant Figures (SF)

The accurately known digits in a number plus one

uncertain digit are called its significant figures.

Two accurately known digits

One uncertain digit

SF=2+1=3 13.4 g

Three accurately known digits

One uncertain digit

SF=3+1=4 13.40 g


Number of SF rules

1. All nonzero digits are significant

2. Leading zeros to the left of the first nonzero digit

are not significant

3. Trailing zeros that are after the decimal point are

significant

0.001 m

0.012 m

0.001m= 1*10-3 m=

1.234 m

3.07 m

3.20 m

0.0320 m

Reason? 1mm (definitely SF=1)

SF=3 SF=3

SF=4

SF=3

SF=1 SF=2


Number of SF rules (cont.)

4. When a number ends in zeros that are not to the

right of a decimal point, the zeros are not

necessary significant.

Here, there is an ambiguity:

length=2950 m, SF may be 3 and 4 ? To avoid ambiguity powers-of-10 notation is used

(reasonable convention):

If you mean that SF=3, write 2.95x103 m

If you mean that SF=4, write 2.950x103 m


Addition/Subtraction/Multiplication/Division

• In addition/subtraction, the final result is no more precise than

the least precise number used to get the answer.

• In multiplication/division, any number of the problem with the

least number of SF determines the number of SF in the

answer.

82 kg + 0.13kg = Least certain

82.0kg + 0.13kg = Least certain

82.00kg+0.13kg = Both equally certain

82.000kg+0.13kg= Least certain

3.0 x 12.60 =

82.13kg

=82.1kg

82.13kg

82.13kg

37.80 = 38 (SF=2) (SF=4)

82 kg + 0.93kg = 83kg =82kg 82.93kg

82.13kg

(SF=2 should be)


Units

• Units are important !

– “It weighs 5 “ ? Could mean:

– “It weighs 5 ton”

Or….

– “It weighs 5kg”

• In Physics we try to use same set of units:

SI: Système Internationale

5 ton 5 kg


SI units (cont.)

• Length: meters [m]

• Time: seconds [s]

• Mass: kilogram [kg]

• Temperature [K]

For very small or very large numbers, use prefixes:

Ggiga109

Mmega106

Kkilo103

mmilli10-3

µmicro10-6

nnano10-9

• 100,000m can also be written as 100 kilometers (km)

• 0.0001s could be written as 100 microseconds (µs)


Converting units

Very often we have to convert a quantity in a certain unit to its equivalent

in a different unit of the same kind.

In this case, we use the fact that multiplying anything by 1

doesn’t affect its value:

Example: Convert 30mile/h to m/s


Example: calculating the distance

to a lightning strike

Estimating

Being able to make order of magnitude estimates is an important skill!!


What is the weight of the earth?

Estimating


The End

See you on Monday