Dr. SoerenPrell A417 ZaffaranoHall 294-3853 [email protected]/phys111/lectures/Soeren/Lect_01.pdf · (the Scientific Method) Observe and measure check Build

Dr. Soeren PrellA417 Zaffarano Hall

[email protected]

Office Hours: by appointment (just send me a brief email)

Today’s Topics:

• Course structure

• Mathematical Concepts (Giancoli 1:1-8)

– Units and Unit Conversions– Dimensional Analysis– Significant figures– Conversions

About myself

Office hours: by appointment

• Dr. Soeren Prell– Office: A417 Zaffarano– Phone: 294-3853– E-mail: [email protected]

• Courses taught at ISU (since 2002)– Introduction to Classical Physics I + II– Modern Physics Lab – Quantum Mechanics I + II– General Physics I

• Research– Experimental elementary particle physics

at the Large Hadron Collider (LHC)

• Hobby– Judo coach at Cyclone Martial Arts Club

The Physics 111 Team

• Lecturers: – Dr. Soeren Prell

• Lab supervisor– Dr. Paula Herrera

• Course secretary– Deb Schmidt

• Recitation and Lab Teaching Assistants:– Anatoli Frishman, Andrew Goenner, Mengyao Huang,

Shreeram Jawadekar, Kyungchan Lee, Soham Pal, Cory Schrandt

Canvas and Course Web SiteCanvas– Announcements– Grades– Link to Phys 111 Course Web Page

(for back-up, if Canvas does not cooperate)

Posted material– Syllabus– Lecture notes– HW, quiz and worksheet solutions– Exam locations and schedule– Exams and solutions, old exam archive– Etc.

courses.physics.iastate.edu/phys111/homepage.htm

The syllabus• Linked from Canvas and from Phys 111 course web page

(under Course Info)– http://course.physastro.iastate.edu/phys111/

• Lecturer contact information • Info on textbook and other course material

– Incl. for online homework• Course schedule

– Lectures, recitations, hw assignment due dates (online hw and reading), quizzes, exams, etc.

• Grading policyFirst homework assignment:

read the syllabus carefully!

Exams

• 3 mid-semester exams– Evening exams at

• Final exam

Tuesday, February 6 8:15 pm – 9:45 pmTuesday, March 6 8:15 pm – 9:45 pmTuesday, April 10 8:15 pm – 9:45 pm

May 1 – 5 day and time TBA, 120 minutes

Make no other plans for these evenings !

Recitations

• Each Friday (50 minutes)

– Worksheet (40 minutes)• Hands-on, interactive learning

– Quiz (10 minutes)

Labs• Read detailed lab info on Canvas under

PHYS 111 LABS (Spring 2017)– 14 two-hour labs– Each section meets every week– Prelab must be completed before corresponding lab– Check lab schedule for dates & time of your session

• For any questions regarding labs, e-mail Dr. Paula Herrera ([email protected]).

Questions based on material covered in recitations and labs will be on the exams !

Student Assistance

• Physics 111 help room (= TA office hours)– Room 53 Physics

• Lecturer office hours• Physics 111 course web site and info on

Canvas• SI session for Physics 111

How to succeed in Physics 111Physics can only be learned by doing it

(just like swimming or juggling)

• Lectures– Prepare for lecture

• Read the indicated assignments before class – Attend classes actively

• Ask questions, participate in interactive problems

• Homework and worksheets– Do all problems– Review the solutions– Understand concepts and learn from your mistakes

• Don’t fall behind !

Lectures• Turn off your and put away your cell phone• Laptops are discouraged in lecture• No need to bring your textbook• Note taking encouraged• Lecture notes will be posted on the course web

page after each lecture• Occasionally, there will be a short quiz in class for

extra credit (You get half the possible points just for taking the quiz.)

Questions?????

Lecture 1Scientific method,units, dimensional analysis, significant figures

How Physics works(the Scientific Method)

Observe and measure

check

Build a model

Make a prediction

Units• Fundamental quantities

– Length or distance [L], time [t] and mass [m] + others to be named at a later date.

• Derived quantities– Combinations of the above quantities

• e.g. speed or velocity are specified in terms of [L]/[t]

But since there are several systems, you may need to convert between units

Some common unit conversions

1 ft = 0.3048 m

1 mi = 1,609 m

1 hr = 3600 sec

1 day = 24 hrsMore unit conversions are listed on the backside of Giancoli’s cover page

The only countries not using the metric system are the US, Liberia and Myanmar.

For example, given that 1 m = 3.28084 ft, this 8611-m mountain is 28251 feet high.

ExampleWhen my son was born, he measured 21 inches long. What is this value in centimeters?

1 inch = 2.54 cm

So, (21 inch) x 2.54 cm = 53.34 cm1 inch

How many meters?1 m = 100 cm

So, 53.34 cm x 1 m = 0.5334 m100 cm

Anyone have any problem with my answers?

Conversion Factors

Precision!... Significant digits.Least precise quantity determines precision.

53 cm

0.53 m

Problem solving strategies

1) In all calculations, write down the units explicitly.

Dimensional Analysis

Velocity, speed (v): [L]/[t] e.g. meters/sec.

Acceleration (a): [L]/[t]2 e.g. meters/sec.2

Force (F) : [m][L]/[t]2 e.g. kg-meters/sec.2

Dimension ≡ physical nature of a quantity and the type of unit used to specify it.

Length [L], time [t] and mass [m]

1) Dimensions on both sides of “=“ must be consistent2) Only quantities with same dimension can be added or

subtracted

Are the following equations dimensionally correct?

221 vtx =

[ ] [ ] [ ][ ]tLttLL 2 =úûù

êëé=

221 atx =

[ ] [ ] [ ]LttLL 22 =úûù

êëé=

Problem solving strategies1) In all calculations, write down the units

explicitly.2) If you carry your units along…you can check

whether the dimensions are correct and consistent

Trigonometry

hho=qsin

hha=qcos

a

o

hh

=qtan

hho1sin-=q

hha1cos-=q

a

o

hh1tan-=q

Pythagorean theorem: 222ao hhh +=

ExampleThe gondola ski lift at Keystone, Colorado is 2830 m long. On average, the ski lift rises 14.6° above the horizontal. How high is the top of theski lift relative to the base?

H

θ

h

sin θ = H/h

H = h sin θ = (2830 m) sin 14.6° = 713 m

Problem solving strategies1) In all calculations, write down the units

explicitly.2) If you carry your units along.. You can check

whether the dimensions are correct and consistent

3) Draw a figure and label it regardless of how simple the problem may appear! Most times you will have to determine relationships between variables. Visualization makes all the difference!

A tougher one

35.0°

85.0 m

38.0°

85.0 m

(a) (b)

Ha

Hb

How tall is the antenna itself?

( ) ( )a b85.0 m tan35.0 and 85.0 m tan38.0H H= ° = °

( ) ( )b a 85.0 m tan 38.0 85.0 m tan 35.0 6.9 mH H- = °- ° =

Problem solving strategies1) In all calculations, write down the units explicitly.2) If you carry your units along.. You can check whether the

dimensions are correct and consistent3) Draw a figure and label it regardless of how simple the problem

may appear! Most times you will have to determine relationships between variables. Visualization makes all the difference!

4) Even with all of the formulas in front of you, there is (almost) always a critical relationship or condition that you must satisfy….Think before you solve!

Required MATH

• Algebra (esp. solving 2 equations with 2 unknowns)

• Trigonometry• Exponentials and logarithms• No calculus

We will visit (or revisit) vectors in the 4th lecture.

ACT: Algebra

A = BC/(D+E)1. E = BC/A + D2. E = BC/A – D3. E = BC/AD

SIGNIFICANT FIGURES

For calculations involving more than one parameter, the number of significant figures is determined by the least precise parameter

ex. x = 6.23 mt = 2.3 s

v = x / t = 2.7087 m/s → 2.7 m/s

ACT: Significant figures

v = x / t = 5.358 m / 2.01 s = 2.66567 m/s

1. v = 2.66 m/s2. v = 2.67 m/s3. v = 2.665 m/s4. v = 2.666 m/s

SCIENTIFIC NOTATION

ex. A = 35,000,000= 3.5 x 107

ex. B = 0.0000035= 3.5 x 10-6

ACT: Scientific notation

B = 0.00021

1. B = 2.1 x 10-2

2. B = 2.1 x 10-3

3. B = 2.1 x 10-4

4. B = 2.1 x 10-5

Standard prefixes for the decimal system

These are the standard SI prefixes for indicating powers of 10.

Many are familiar; Y, Z, E, h, da, a, z, and y are rarely used.