Physics 1A: Introduction to Physics

and Problem Solving

Instructor: Dr. Rae RobertsonLectures: MTWThF 8:00 - 9:20 AM

Course LogisticsLectures: MTWTHF 8:00 - 9:20 AM, WLH 2005

Problem Sessions: Th 2:00 - 3:20 PM, WLH 2204TA: James Wilson, wilsja@gmail.com

Instructor Office Hours: Th 9:30 - 11:30 AM, MH 2661TA Office Hours: W 2:00 - 4:00 PM, Physics Tutorial Center (Mayer

Hall)

Course Webpage: http://physics.ucsd.edu/students/courses/summer2008/managed/physics1a/

Textbook: College Physics, Vol I, Serway & Faughn

Grading: Final: 40%, Quizzes: 60% (20% each), Questions of the Day: 20%, Weekly Homework Sets: Ungraded

NO makeup quizzes or Final! Know your student code!

Lecture Attendance: Mandatory! You can’t learn unless you show up.

Please bring 3x5 notecard to each lecture for daily questions.

What is Physics??

The most incomprehensible thing about the world is that it is comprehensible.

-Albert Einstein

Observations, Theories & Predictions

Physics

TheoryExperiment

Careful observations and recording

of physical phenomena

Systematic variation of conditions

Testing theoretical predictions

Formulation of general descriptions of physical

phenomena

Predictions about physical phenomena at all conditions

Problem Solving

Understanding HOW physical systems/phenomena work and

WHY it behaves as it does

Mathematics: The Language of Physics

The Book of Nature is written in mathematical characters, without whose help it is impossible to comprehend a single

word…..-Galileo

Descriptions of physical phenomena = mathematical equations

Variables = physical quantities/characteristics of system

E = mc2

EnergyMass

Speed of Light (3*109 m/s)

Mathematics: The Language of Physics

The Book of Nature is written in mathematical characters, without whose help it is impossible to comprehend a single

word…..-Galileo

Descriptions of physical phenomena = mathematical equations

Variables = physical quantities/characteristics of system

F = ma

ForceMass

Acceleration

Dimensions and UnitsMany ways to describe an object or system

Dimension = physical nature of quantity

Three fundamental dimensions can be used to describe many types of phenomena/physical systems

LENGTH

Size of an object

Distance between objects or events

SI UNIT = METER

MASS

How much matter is in an object

SI UNIT = KILOGRAM

TIME

How long something lasts

SI UNIT = SECOND

Dimensional Analysis

L*L*L = L3

[m] = M[x] = L

[t] = T

Volume [V] =

Velocity [v] = [x]/[t] L/T

Acceleration [a] = [v]/[t] (L/T)/T = L/T2

Force [F] = [m]*[a] = M*L/T2

m3

m/s

m/s2

kg*m/s2 = N

Physical Quantity Dimension SI UnitVERY IMPORTANT IN PROBLEM SOLVING!!!

Unit Conversion

A = 10 m2 3.28 ft

X m

1 m = 3.28 ft = 39.37 in1 mile = 1609 m = 1.609

km

What is X in meters?

What is X in feet?

What is the speed limit in SI units?

Coordinate Systems

+

+

-

-

O

++

-

-

O

Coordinate Systems

Cartesian Coordinates Polar Coordinates

Point in space specified by distancefrom origin in x and y directions

P = (x,y)

Point in space specified by straight line distance from origin

and angle of line P = (r,)

Trigonometry Review

x

y

X

Y

r

Pythagorean Theoremr2 = x2 + y2

Sin = side opposite hypotenuse

side adjacent to hypotenuse

side opposite side adjacent to

yr

xr

yx

Cos =

Tan =

=

==

Trig Functions

Sin-1 (y/r) =

Cos-1 (x/r) =

Tan-1 (y/x) =

Inverse Trig Functions

YOU WILL USE THESE OVER AND OVER AND

OVER AND OVER AGAIN!!

GET USED TO THEM!!!

Problem Solving:10 fool-proof steps

1) READ2) READ AGAIN

3) DRAW DIAGRAM4) CHOOSE/LABEL COORDINATE SYSTEM

5) LABEL PHYSICAL QUANTITIES

6) IDENTIFY ALL KNOWN & UNKNOWN QUANTITIES7) CHOOSE EQUATIONS

8) SOLVE EQUATIONS

9) INSERT KNOWN QUANTITIES10) CHECK!!

Questions of the Day

1) If an equation is not dimensionally correct, does that mean that the equation can’t be true?

A) YESB) NO

2) You walk 10 m in a direction 20o North of East, you want to know how far North you have

traveled…What trig function would you use to figure this out?

A) Sine B) Cosine

C) Tangent