# Physics 1A: Introduction to Physics and Problem Solving by G8n2Pd

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```									        Physics 1A:
Introduction to Physics
and Problem Solving

Instructor: Dr. Rae Robertson
Lectures: MTWThF 8:00 - 9:20 AM
Course Logistics
Lectures: MTWTHF 8:00 - 9:20 AM, WLH 2005
Problem Sessions: Th 2:00 - 3:20 PM, WLH 2204
TA: James Wilson, wilsja@gmail.com
Instructor Office Hours: Th 9:30 - 11:30 AM, MH 2661
TA 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%,
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

Experiment                                   Theory
Careful observations and recording      Formulation of general descriptions of
of physical phenomena                     physical phenomena

Systematic variation of conditions             Predictions about physical
phenomena at all conditions
Testing theoretical predictions

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
Speed of Light
Energy                               (3*109 m/s)
Mass
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
Acceleration
Force
Mass
Dimensions and Units
Many 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
MASS                                                    TIME
LENGTH

Size of an object

Distance between                  How long
How much matter                                           something lasts
objects or events
is in an object
SI UNIT = METER           SI UNIT = SECOND
SI UNIT = KILOGRAM
Dimensional Analysis

[x] = L
[m] = M                                      [t] = T

VERY IMPORTANT IN Unit
Physical QuantityDimension  SI

PROBLEM SOLVING!!!m
Volume [V] =  L*L*L = L              3          3

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

Acceleration [a] = [v]/[t]   (L/T)/T = L/T2      m/s2

Force [F] = [m]*[a] =          M*L/T2          kg*m/s2 = N
Unit Conversion
1 m = 3.28 ft = 39.37 in
1 mile = 1609 m = 1.609 km

A = 10 m2            3.28 ft

Xm

What is X in meters?
What is the speed limit
in SI units?
What is X in feet?
Coordinate Systems

+

-   O      +
-
Coordinate Systems
Cartesian Coordinates                   Polar Coordinates

Point in space specified by
Point in space specified by distance
straight line distance from origin
from origin in x and y directions
and angle of line
P = (x,y)
P = (r,q)
Trigonometry Review
Trig Functions
Y                      Sin q =      side opposite q       = y
hypotenuse            r
YOU WILL USE THESE
r         Cos q = side adjacent to q
AND
OVERyAND OVER hypotenuse                                x
= r

q
OVER AND OVER q
Tan q =   side opposite                    =   y
x   AGAIN!!
X

Inverse Trig Functions

Sin-1 (y/r) = q
GETy USED TO THEM!!!q
Pythagorean Theorem
2   2
r =x +   2     Cos (x/r) =          -1

Tan-1 (y/x) = q
Problem Solving:
3) DRAW DIAGRAM
10 fool-proof steps
4) CHOOSE/LABEL COORDINATE SYSTEM
5) LABEL PHYSICAL QUANTITIES
6) IDENTIFY ALL KNOWN &
UNKNOWN QUANTITIES
7) CHOOSE EQUATIONS
8) SOLVE EQUATIONS
9) INSERT KNOWN QUANTITIES
10) CHECK!!
Questions of the Day
1) If an equation is not dimensionally correct, does that
mean that the equation can’t be true?

A) YES
B) 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

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