Lecture 1, 8 24 11 - University of Miamirads.physics.miami.edu/optics/ken/CLASS101_F_11_old/Lecture...

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PHYSICS 101

  Dr. Kenneth Voss, Dr Joseph Ashkenazi

  Rm 304 / 310 Physics Building   Web page access, through physics department:

  www.physics.miami.edu, then into either my or Dr. Ashkenazi’s pictures

  Entire class will be graded together, one exam, so attend either lecture.

  Check out Syllabus:   http://phyvax.physics.miami.edu:8001/ashkenazi/101/syl.htm

  Quizzes each week in the Discussion sections

Important items from syllabus

  Mondays, Sept 19, October 17, November 14

  Exams in the evening 5 – 6:15 Final Monday Dec 12, 8 – 10:30 PM

Grades: 20% each mid term, 40% final

20 % Homework (8%), Quiz (6%), and Clicker questions (6%).

Drop lowest 20% (can be half of final) Drop lowest homework score, quiz, and 5 lowest clicker scores…covers missed days..forgotten clickers, etc.

Mastering Physics

  Why do we do homework?

  Homework is not for us…we know it already   The only way to learn physics is by doing problems and thinking

about it

  Doing problems helps test your understanding

  Mastering physics used to allow a more careful check of your homework, so you know if you are doing it right.

  It also has tutorial to try to help if you don’t understand.   It is part of your grade because we think it is important that you do

the problems

  Exam problems will be very similar to the assigned (and suggested problems look at homework sheet:

  Instructions to register Mastering physics on web page

Homework Sheet

  http://phyvax.physics.miami.edu:8001/ashkenazi/101/hw1.htm

  Note suggested problems and assigned problems.   We have looked at these to make sure they are relevant and help

you.

  Having problems? Do extra ones like these, odd number problem answers in back of book.

  When studying for exam, don’t just look at homework assignments/problems/examples…actually do them out again

  The more you practice, the better you will be in this exam and the MCAT or whatever your goal is.

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Class record sheet

  http://phyvax.physics.miami.edu:8001/ashkenazi/101/display_grades.html

  This will be your way to check your grade. Don’t wait until Dec 11 to check.

Grade scale   A+ 98% A 93% A- 89%

  B+ 85% B 78% B- 73%   C+ 68% C 60% C- 55%

  D 45%

  This is the maximum grading scale…some parts might shift down (for example B to 75%) if necessary because of a test that turns out harder than we expected.

Clickers

  http://phyvax.physics.miami.edu:8001/ashkenazi/101/Clickers.htm

  Above has links to two articles, one from the Herald and one in Science magazine.

  We will be using iClickers this semester. We are using these because research in the Physics Education Research (PER) community has shown that they are a very effective tool to increase student learning and comprehension when used properly.

  Part of using clickers will be to test class understanding of conceptual ideas, allow peer interaction, and give me feedback on what you do/do not understand.

  Clicker questions will be part of your grade. Will average all of one days answers into a single day’s score.

  In survey’s, when done right, 90%+ of the students enjoyed the process and over 77% thought they learned more because of them

  IF A STUDENT IS FOUND WITH TWO REGISTERED CLICKERS IN CLASS, THE PENALTY IS THAT THEY WILL BE IMMEDIATELY FAILED FOR THE CLASS.

Registering Clickers

  We will start clickers next Tuesday.

  Register your clicker by going to www.iclicker.com   Need to put in:

  Your last name

  First name (use the name that is on the rolls   C#

  Number from back of clicker

Sources of Help

  ATTEND CLASS…someone is paying your tuition bill, take advantage of it.

  Physics Academy: Monday –Thursday 2-4, 5-7, Rm 105

  Graduate student sitting there to answer questions…make him work……

  Our office hours, listed on Syllabus

  Tutoring available free at the UM Academic resource Center:

  http://www.umarc.miami.edu/arc/Tutoring-Policies.html

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Copyright © 2010 Pearson Education, Inc.

Units of Chapter 1

•  Physics and the Laws of Nature

•  Units of Length, Mass, and Time

•  Dimensional Analysis

•  Significant Figures

•  Converting Units

•  Order-of-Magnitude Calculations

•  Scalars and Vectors

•  Problem Solving in Physics


1-1 Physics and the Laws of Nature

Physics: the study of the fundamental laws of nature

•  these laws can be expressed as mathematical equations.

• In understanding physics, very hard to avoid mathematics, but we also want you to understand conceptually what is going on.

•  much complexity can arise from relatively simple laws


1-2 Units of Length, Mass, and Time SI units of length (L), mass (M), time (T): Length: the meter Was: one ten-millionth of the distance from the North Pole to the equator Now: the distance traveled by light in a vacuum in 1/299,792,458 of a second Mass: the kilogram One kilogram is the mass of a particular platinum-iridium cylinder kept at the International Bureau of Weights and Standards, Sèvres, France. The one standard not tied to a physical phenomena Time: the second used to be a fraction of a day Now:One second is the time for radiation from a cesium-133 atom to complete 9,192,631,770 cycles.


1-2 Units of Length, Mass, and Time

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1-3 Dimensional Analysis

•  Any valid physical formula must be dimensionally consistent – each term must have the same dimensions

From the table:

Distance = velocity × time

Velocity = acceleration × time

Energy = mass × (velocity)2

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1-4 Significant Figures

•  accuracy of measurements is limited

•  significant figures: the number of digits in a quantity that are known with certainty

•  number of significant figures after multiplication or division is the number of significant figures in the least-known quantity

• Just because your calculator shows 9 digits doesn’t mean these digits mean anything.


Example: A tortoise travels at 2.51 cm/s for 12.23 s. How far does the tortoise go?

Answer: 2.51 cm/s × 12.23 s = 30.7 cm (three significant figures)




Scientific Notation

•  Leading or trailing zeroes can make it hard to determine number of significant figures: 2500, 0.000036

•  Each of these has two significant figures

•  Scientific notation writes these as a number from 1-10 multiplied by a power of 10, making the number of significant figures much clearer:

2500 = 2.5 × 103

If we write 2.50x103, it has three significant figures

0.000036 = 3.6 x 10-5



Round-off error:

The last digit in a calculated number may vary depending on how it is calculated, due to rounding off of insignificant digits

Example:

$2.21 + 8% tax = $2.3868, rounds to $2.39

$1.35 + 8% tax = $1.458, rounds to $1.49

Sum: $2.39 + $1.49 = $3.88

$2.21 + $1.35 = $3.56

$3.56 + 8% tax = $3.84

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1-5 Converting Units

Converting feet to meters:

1 m = 3.281 ft (this is a conversion factor)

Or: 1 = 1 m / 3.281 ft

316 ft × (1 m / 3.281 ft) = 96.3 m

Note that the units cancel properly – this is the key to using the conversion factor correctly!


This was hopefully the last lecture I will give For next week, before class Be prepared for: Tuesday Sections 2.1 – 2.4 Thursday Sections 2.4-2.6 There will probably be a quiz on this material to start class.

Lecture 1, 8 24 11 - University of Miamirads.physics.miami.edu/optics/ken/CLASS101_F_11_old/Lecture...

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