PH 211 Winter 2014
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New course offering (also PH212 in Spring)
Lab room Weniger 204
Syllabus has rules of the course
Syllabus has daily schedule, midterms, labs
Web-site has lab material
Web-site:
www.physics.oregonstate.edu/~jansenh/COU
RSES/ph211
Registering your clicker:
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BEFORE SUNDAY January 12th, register
your clicker on BLACKBOARD using your
clicker ID number on the back of the device
(a 6 digit alphanumeric ID)
•
(We will test clickers Wed and Fri – but
no points will be given until week 2)
• MasteringPhysics code: MPJANSEN95607 - INPUT
YOUR STUDENT ID – NO SPACES!!!
• Lab Excuses: If you have taken 211 within the past 2
years and received a D- or better (and completed
all of the labs), you can ask to be excused from the
lab (you do need to remain registered): Email me
your name, ID#, when you took lab, and your
grade and I will confirm the lab excuse. for
• LAB STARTS Thursday, RECITATION STARTS WEEK 2
• 1st hmwk is Chpt 3 – math review, ONLINE ONLY,
due Monday at 2 before midnight– IS POSTED
Labs
Go to
http://www.physics.oregonstate.edu/~jansenh/
COURSES/ph211/LABS/index.html
Read Instructions in section A ahead of time.
Lab 1 instructions will be on the lab computers.
Google moderator
Try a new tool (need google login):
Which topic would you like to discuss in class on
Friday?
https://www.google.com/moderator/#16/e=20f
7a8
Do your voting question points
depend on whether or not your
answer is ‘correct’?
CHANNEL 42
1. Yes
2. No
Do your voting question points depend
on whether or not your answer is
‘correct’?
CHANNEL 42
1. Yes
2. No
71%
o
N
Ye
s
29%
Where can you go for help?
1.
2.
3.
4.
Weniger help room, 12-6 MTWRF
Library help room, 6-10, SMTWR
Professor office hours
Discussion board (blackboard)
What is a vector?
• Set of instructions in the form move two chairs to
the left
• Anything with a length and direction
• A picture like
• An ordered set (L,dir) with L ≥ 0
• A formal mathematical concept, defined by
addition, multiplication by scalar, zero, and
inversion
• All of the above
Which figure most accurately represents the
addition of vectors A and B?
A
1.
2.
3.
4.
Figure One
Figure Two
Figure Three
Figure Four
B
A+B
A+B
Figure 1
Figure 2
A+B
Figure 3
A+B
Figure 4
Which figure most accurately represents the
addition of vectors A and B?
Figure 1
Figure 2
Figure 3
Figure 4
A
B
A+B
A+B
Figure 1
Figure 2
97%
A+B
ur
e
Fig
ur
e
Fig
4
1%
3
1%
2
ur
e
Fig
ur
e
1
2%
Fig
A.
B.
C.
D.
Figure 3
A+B
Figure 4
In order to agree on statements
about vectors we need to agree
on how we measure length and
direction!
Unit of length: meter
Vectors and components
𝑎 = 𝑎𝑥 + 𝑎𝑦
Vectors and components
𝑎 = 𝑎 𝑥 + 𝑎𝑦 = 𝑎𝑥 𝑖 + 𝑎𝑦 𝑗
Note that 𝑎𝑥 can point in the plus
or minus î direction. We include the
sign in the number 𝑎𝑥
Vectors and components
𝑎 = 𝑎 𝑥 + 𝑎𝑦 = 𝑎𝑥 𝑖 + 𝑎𝑦 𝑗
Book always writes
(length, direction)
Common notation
(𝑎𝑥 , 𝑎𝑦 )
An old clock
The minute hand of a clock is 17.5 cm long.
What is the vector connecting the tip of the
minute hand at 8:00 am and 8:20 pm?
What is the vector connecting the tip of the
minute hand at 8:00 am and 11:00 pm?
What is the sum of these four vectors?
Which of the following mathematical
statements is correct?
1.
2.
3.
4.
Ctan(Θ) = A
Ccos(φ) = A
Csin(Θ) = B
Csin(Θ) = A
C
A
Θ
B
Φ
Which of the following mathematical statements is
correct?
A. C tan(Θ) = A
B. C cos(φ) = A
C. C sin(Θ) = B
D. C sin(Θ) = A
C
A
Θ
B
Φ
Quantitative addition/subtraction
• Writing the vector in terms of its components using
trig functions
• Writing the length of a vector given its components
• Writing the vector using unit vector notation
• Writing vector sums using components
• Write the vector (A-B) using at least 3 different
mathematical representations
Example problem 3.40
The treasure map in the figure gives the
following directions to the buried
treasure: "Start at the old oak tree, walk
due north for 500 paces, then due east for
100 paces. Dig." But when you try that
path you find an angry dragon by the tree.
To avoid the dragon, you set off along the
yellow brick road at an angle 60o east of
north. After walking 300 paces you see an
opening through the woods. Which
direction should you go and how far in
order to reach the treasure?
Finding angle between vectors
Vector A: (3,4) and Vector B: (2,8)
Find the angle for each individual vector, and find
the angle between the vectors
Finding angle between vectors
Vector A: (3,4) and Vector B: (2,8)
Dot product: 𝐴 ∙ 𝐵 = 𝐴𝑥 𝐵𝑥 + 𝐴𝑦 𝐵𝑦 + 𝐴𝑧 𝐵𝑧
Dot product: 𝐴 ∙ 𝐵 = 𝐴
𝐵 cos(𝜃)