Transcript Physics 1A: Introduction to Physics and Problem Solving

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, [email protected]
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%,
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
Experiment
Theory
Careful observations and recording
of physical phenomena
Formulation of general descriptions of
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
Energy
Mass
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
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
How much matter
is in an object
SI UNIT = KILOGRAM
Distance between
objects or events
How long
something lasts
SI UNIT = METER
SI UNIT = SECOND
Dimensional Analysis
[m] = M
[x] = L
[t] = T
VERY IMPORTANT
INSI Unit
Dimension
SOLVING!!!
VolumePROBLEM
[V] =
L*L*L
=L
m
Physical Quantity
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 X in feet?
What is the speed limit
in SI units?
Coordinate Systems
+
-
O
+
-
Coordinate Systems
Cartesian Coordinates
Point in space specified by distance
from origin in x and y directions
P = (x,y)
Polar Coordinates
Point in space specified by
straight line distance from origin
and angle of line
P = (r,q)
Trigonometry Review
Trig Functions
Sin q =
side opposite q
hypotenuse
YOU WILL USE THESE
side adjacent to q
r
Cos
q
=
OVERyAND OVER hypotenuse
AND
OVER
AND
OVER
side opposite q
q
Tan q =
side adjacent to q
X
AGAIN!!
x
Inverse Trig Functions
Sin-1 (y/r) = q
GET
USED
TO
THEM!!!
Cos (x/r) = q
r =x +y
Pythagorean Theorem
2
2
2
-1
Tan-1 (y/x) = q
= y
r
x
= r
=
Y
y
x
1) READ
2) READ AGAIN
3) DRAW DIAGRAM
4) CHOOSE/LABEL COORDINATE SYSTEM
5) LABEL PHYSICAL QUANTITIES
Problem Solving:
10 fool-proof steps
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