Physics 114
Professor Fred Salsbury
Office Hours: MWF 11-11:40am; M 1-2pm
301A Olin
http://www.wfu.edu/~salsbufr
http://www.webassign.net
salsbufr@wfu.edu
Topics Covered
•Electricity and Magnetism
•E&M Waves
•Nuclear Physics
Please Pick Up and READ the
Course Policy &Syllabus
Class Participation
•Cut out your voting cards and bring them to every class
•If you forget them, borrow some from me
•If you lose them, get new ones from me
•We will be using them for Concept quizzes in-class
Reading Assignments and Quizzes
Reading Assignments
Required:
Every Lecture starting Wed; quizzes cover
Recommended:
Applications
Online exercises
Extra:
More rigorous mathematical treatments
Recommended and Extra will be on reserve at the library
Along with two mathematics review texts.
Reading quizzes,
due 7am before every lecture; starting Wed
A few submissions per problems
Work by yourself
Homework and Semester Quizzes
Homework Assignments
Required:
Every Lecture Starting Friday
Several Submissions
Encouraged to work with others, but
you must submit your own work.
Semester quizzes
Four – see syllabus for datyes
Lowest score is weighted ½
Grading
Final Exam
Semester Quizzes
Laboratory ,Homework
Reading Quizzes
Total
330 points
350 points
and
320 points
1000 points
You must pass lab to pass the course.
You are expected to pass the final.
If you miss any semester quiz or exam, I need a note from a
medical doctor or the Dean’s office.
Webassign
•http://www.webassign.net/student.html
•Username is your email (without @wfu.edu)
•Institution is wfu
•Password (if new to webassign) is your student number
•If you have used webassign before use your old password.
There is a test homework
on using webassign.
Log into webassign ASAP.
If you have difficulty, contact me.
Web Information
How to access course info:
•Go to www.wfu.edu/~salsbufr
•Click on teaching
•There will be a page for general announcements, and a sidebar
filled with useful information; including lecture notes.
•This course does not use blackboard.
Survey
•Online at webassign
•Worth 2 points if completed
•Due Wednesday
•To provide me with a idea of your
backgrounds and expectations, and
tutorial times.
Coordinate systems
Different ways of representing space, and physics.
Some problems are easier in some coordinate systems,
but the physics is invariant.
Cartesian Coordinates:
Polar Coordinates
Another popular coordinate system, along with cylindrical
and spherical
x  r cos 
y  r sin 
y
tan  
x
r x y
2
2
Vectors and Scalars
Vectors: Magnitude and direction
Scalars: Magnitude
Displacement is a vector.
Velocity is a vector.
Acceleration is a vector.
Vector Components: Geometric
The x- and y-components of a
vector:
Ax  A cos 
Ay  A sin 
The magnitude of a vector:
A
Ax  Ay
2
2
The angle  between vector and x-axis:
 Ay 
  tan  
 Ax 
1
Vector Components: Algebraic
•
•
•
•
A unit vector is a dimensionless vector having a magnitude 1.
Unit vectors are used to indicate a direction.
i, j, k represent unit vectors along the x-, y- and z- direction .
x̂, ŷ, ẑ is another common notation.
• i, j, k form a right-handed coordinate system.
A = Axi + Ayj
Vector Addition: Algebraic I
We want to calculate:
R=A+B
From diagram:
R = (Axi + Ayj) + (Bxi + Byj)
R = (Ax + Bx)i + (Ay + By)j
The components of R:
Rx = Ax + Bx
Ry = Ay + By
Vector Addition: Algebraic II
The magnitude of R:
R  Rx  Ry  ( Ax  Bx ) 2  ( Ay  B y ) 2
2
2
The angle  between vector R and x-axis:
 Ry
tan   
 Rx
  Ay  By
  
  Ax  Bx



Vector Multiplication
There are two ways (in 2 or 3D) to multiply vectors.
Scalar product -> two vectors make a scalar
 
A B  N
Also called the dot product
or the inner product
Vector product -> two vectors make a vector
  
A B  C
Also called the cross product
or the outer product
Scalar Product
Scalar product -> two vectors make a scalar
 
A  B  ab cos
Geometric
 
A  B  axbx  a y by  az bz
Algebraic
Vector Product
Vector product -> two vectors make a vector
  
A B  C
Geometric
C has magnitude absin. Direction perpendicular
to the plane containing A and B.
Algebraic
 
A  B  (a y bz  by az )i  (az bx  bz ax ) j  (axby  bx a y )k
The right hand rule
Force F
velocity v
Magnetic
Field B

F  q vB

F  qvB sin 
Electricity and Magnetism
•One of the four fundamental forces of nature
•Responsible for the vast majority of what we observe around us
•Probably best-understood and best-tested of the forces of nature
Electromagnetic Interactions:
•Electricity and Electronics
•Magnetism
•Chemistry
•Biology
• and even more
Electrical Charges
•Electric forces only affect objects with charge
•Charge is measured in Coulombs (C). A Coulomb is a lot of
charge!
•Charge comes in both positive and negative quantities
•Charge is conserved – it can neither be created nor destroyed
•Charge is usually denoted by the letter q.
An object has a total charge of 5 mC. It is divided
into two pieces, one of which has charge 8 mC
and the other of which has charge
A) 3 mC
B) -3 mC
C) 13 mC
D) Such a division is impossible
Matter and Charges
•All matter is made of positive and negative charges (or neutral)
•An object’s total charge is very close to zero
•When an object becomes charged, a tiny fraction of its charged
particles (usually electrons) are lost or gained
•These particles (usually electrons) can flow through objects
•Some materials are better at allowing the flow of electrons than
others
Conductor
A material that allows
electrons or other
charged particles to
flow freely
Insulator
A material that resists
the flow of electrons
and other charged
particles
Elementary Charge
•Charges seem to come only in integer multiples of a fundamental
charge unit called e
•We will treat e as a positive number (some sources treat it as
negative)
e = 1.602  10-19 C
Particle
Proton
Neutron
Electron
Oxygen nuc.
Calcium ion
Chlorine ion
q
e
0
-e
8e
2e
-e
know these