Transcript Lecture 01 - Purdue University

Welcome to PHYSICS 220
(Section 2)
Prof. Yulia Pushkar
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Lecture 1
Kinematics
Forces
Energy and Momentum
Rotations
Fluids
Oscillations/Waves/Sound
Thermodynamics
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Textbook
The textbook is College Physics, Vol I,
by Nicholas J. Giordano (Brooks/Cole).
We will cover almost all of the topics in
this volume, at a rate of one chapter
per week!
Very Fast!
Come prepared!
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Course Web Site
http://www.physics.purdue.edu/phys220
• Course Syllabus
– Policies
– Grading scheme
– Exams & iClicker exercises
• Lab Syllabus
• Tentative Class Calendar
– Pre-lecture reading assignments
– Homework due dates
• CHIP User’s Guide
– Homework
– Grades
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Class Format
• Lecture Section 2:
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Time: Monday, Wednesday 11:30 - 12:20
Lecture Room: PHYS 114
Instructors: Prof. Yulia Pushkar
Office Hours: 5 -6 pm on Monday and Wednesday
Office: PHYS 70 Phone: 49-63279 Email: [email protected]
(please include on the subject line: PHYS 220)
• Recitation Section 2:
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Time: Friday 11:30 - 12:20
Instructor: Deepak Pandey Office Hours: Friday: 12:30 AM - 5:30 PM
Office: PHYS 11A Phone: 49-43018 Email: [email protected]
CHIP coordinator: Dr. V.K. Saxena, PHYS 176
• Laboratory:
– Coordinator: Dr. A. Lewicki, Office: PHYS 142
– Lab Room: PHYS 121
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Homework
• We will use CHIP (Computerized Homework In
Physics) for homework assignments
• The homework is due by 10 am on Fridays
• Homework is computer graded
– 100% if completed before the deadline
– 75% if completed within three days of the deadline
– 50% if completed after three days but within one week
of the deadline
– 0% after one week past the deadline
– There is a limit on the number of attempts allowed.
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iClicker
• We will use iClicker for interactive lecture and
recitation exercises
– One point for participating in each exercise
– Two points for each correct answer
• iClicker can be purchased at the Purdue bookstore
• Registration:
– You must register your iClicker on CHIP!
• http://www.physics.purdue.edu/academic_programs/courses/icli
cker_register.pdf
– Deadline: by the end of this week
• We will start to use iClicker next week!
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Exams and Grades
• Exams:
– There will be two midterm exams and one final exam. All exams are
closed-book. The final exam will be cumulative.
– Exam 1: Feb 16, 2011, 6:30 – 7:30 PM
– Exam 2: Mar 29, 2011, 6:30 – 7:30 PM
– Final: TBA (2 hours)
• Grades:
– The final grade will be determined on the following basis:
• 300 points final exam
• 300 points two evening exams (150 points each)
• 150 points laboratory
• 100 points CHIP homework
• 50 points recitation exercises
• 100 points lecture exercises
– No excused iClicker exercises.
– You must pass the lab in order to pass the course.
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Tips
• Pre-lecture reading
– Come to the lectures prepared!
• Things to pay attention to
– Concepts, connections, motivation: Lecture
– Problem solving: Recitation + Homework
– Hands-on lab
• Taking notes
– Lecture notes can be downloaded from the course web site
– But they are sketchy … you need to fill in details in class
• Post-lecture reading
– See if there are still things you do not understand
• Seeking help
– See us during office hours!
– Physics Help Center
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Today’s Lecture
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What is physics?
Problem Solving
Scientific notations and significant figures
Units of measure
Math of Physics
– Algebra, Geometry
– Vectors
• Motion
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Why is it cool to study Physics?
• The science of matter and energy, and the
interactions between them
– Matter and energy are fundamental to all areas of
science
• The study of the natural or material world and
phenomena
– Meaning of physics from the Greek for Nature
• Natural philosophy
– Oldest science
– All scientists were originally physicists
Problem Solving Strategies
• Recognize the key physics principles
– Need a conceptual understanding of the laws, how they are
applied, and how they are interrelated
• Sketch the problem
– Show the given information / include a coordinate system
• Identify the important relationships
– Use the given information and the unknown quantities to
determine what laws apply
• Solve for the unknown quantities
• What does it mean?
– Does the answer make sense?
– Dimentional analysis
Dealing With Numbers
– Scientific notation
– Significant figures
Scientific notation
Number of people leaving on the Earth (2007):
6,600,000,000
or 6.6 x 109
Scientific notation
Prefix
(abbreviation)
Power
of Ten
Peta (P)
1015
Tera (T)
1012
Giga (G)
109
Mega (M)
106
Kilo (k)
103
Hecto (h)
102
Deci (d)
10-1
Centi (c)
10-2
Milli (m)
10-3
Micro ()
10-6
Nano (n)
10-9
Pico (p)
10-12
Femto (f)
10-15
Significant figures – show accuracy
Your height is:
(A) 5.9 ft
(B) 5.90 ft
B is more accurate than A, as its result contains more
significant figures.
Implies that true value lies between 5.89 ft and 5.91 ft
A digit is significant if it is meaningful
with regard to the accuracy of the value
Significant Figures in Calculations
• Multiplying and dividing
– Use the full accuracy of all known quantities when
doing the computation
– After completing the calculation, round the answer to
the number of significant figures present in the least
accurate starting quantity
– Example: 976 x 0.000064 m = 0.062464 m~ 0.062 m
• Due to the 2 significant figures in the 0.000064
Significant Figures
What is the perimeter of a circle of radius 1.2 m?
L = 2r 2x 3.1415926 … x 1.2 = 7.539822 … m
L = 7.5 m
What about:
3.1415 + 0.1 = 3.2415
or
0.1415 - 0.02 = 0.1215?
Ans: 3.2 or 0.12
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Units
• To communicate the result of a measurement for a
quantity, a unit must be defined!
– Defining units allows everyone to relate to the same
fundamental amount.
– Always write down units and carry the units through all of the
calculations.
• We use the SI system
– Length: meter (m)
– Mass: kilogram (kg)
– Time: second (s)
1 meter = 3.281 ft
1 kg = 2.205 pounds
• Dimensional Analysis:
– Both sides of an equation must have the same units.
– Can be used to verify equations, answers.
Example: density [kg/m3]  = m [kg] / V [m3]
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Trigonometry
 Generally will use only right triangles
 Pythagorean Theorem
 r2 = x2 + y2
 Trig functions (r=hypotenuse)
 sin θ = y / r
 cos θ = x / r
 tan θ = y / x
 Trigonometric identities
 sin² θ + cos² θ = 1
 Other identities are given in appendix B and
the back cover
• To find an angle, you need to use the
inverse of a trig function
If sin θ = y/r then
θ = sin-1 (y/r)= ascsin(y/r)
• Angles in the triangle add up to 90°
α + β = 90°
• Complementary angles
sin α = cos β
Vectors vs. Scalars
• A scalar is a quantity that requires only a
magnitude (with unit)
• A vector is a quantity that requires a magnitude
and a direction (is represented by arrows)
Vector Representation
• The length of the arrow indicates the magnitude of the
vector
• The direction of the arrow indicates the direction of the
vector with respect to a given coordinate system
• Vectors are written with an arrow over a boldface letter
• Mathematical operations can be performed with vectors:
add, subtract, multiply by constant.
Adding Vectors
 Draw the first vector
 Draw the second
vector starting at the
tip of the first vector
 Continue to draw
vectors “tip-to-tail”
 The sum is drawn
from the tail of the first
vector to the tip of the
last vector
Adding Vectors Using Components
• Assume you are adding
two vectors:
• To add the vectors, add
their components
Cx = Ax + Bx
Cy = Ay + By
• Then the magnitude
and direction of C can
be determined
Ax = A cos θ; Ay = A sin θ
C  A B