Physics 1A: Introduction to Physics and Problem Solving Instructor: Dr. Rae Robertson Lectures:...
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Transcript of Physics 1A: Introduction to Physics and Problem Solving Instructor: Dr. Rae Robertson Lectures:...
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, [email protected]
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