phy10-5 lec1
TRANSCRIPT
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Physics 10-4General Physics 1 – Lecture + Lab
http://www.desktopwallpapers4.me/digital-art/fire-vs-electricity-5402/
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Physics 10-5 || Ms. Teci Pulido 2
Phy10-5 Course Outline● Measurement
– Significant Figures
– Standard Units (SI)
– Conversion of Units
● Vectors
– Definition of Vectors
– Components of Vectors
– Operations
● Kinematics
– Distance + Displacement
– Speed + Velocity
– Acceleration
● Forces
● Newton's Laws
● Circular Motion
● Waves
● Optics
– Reflection
– Refraction
– Total Internal Reflection
– Ray tracing
– Interference
– Diffraction
Q1 Q3
Q2
Q4
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Physics 10-5 || Ms. Teci Pulido 3http://www.mscd.edu
Why study Physics?• “Physics is the foundation of all engineering and
technology.”
--- Young and Freedman, University Physics
• It’s an adventure! :)
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Physics 10-5 || Ms. Teci Pulido 4
The Nature of Physics
● Observable● Quantifiable● Repeatable
Physics looks for general laws and principles that govern the natural world.
http://en.wikipedia.org/wiki/Physics
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Physics 10-5 || Ms. Teci Pulido 5
Accuracy vs. Precision
http://2.bp.blogspot.com/_hY3nnOaADyA/S-dY106NbII/AAAAAAAAACU/xCksk7gXcsA/s1600/precisionandexactitud.jpg
ACCURATE“correct”
PRECISE“consistent”,
“exact”
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Physics 10-5 || Ms. Teci Pulido 6
Significant Figures● Digits that contribute to a number's
precision or certainty
1 1.0 1.0000
http://www.mds975.co.uk/Images/sundial4.jpg
http://www.shadestation.co.uk/media/thumbs/800x800/media/product_images/Ice-Clock_SideView_PEfw800fh800.jpg
http://img4.uhrcenter.de/images/produkte/xl/1125x1500/15254837719_1.jpg
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Physics 10-5 || Ms. Teci Pulido 7
Significant Figures- the digits that contribute to a number’s
precision or certainty
●Non-zero digits 1.234 4 SF's
● Zeros between non-zero digits 305 3 SF's
● Zeros after the decimal point 1.500 4 SF's
● Zeros between a non-zero digit and the decimal point
2000. 4 SF's
● Zeros before the first non-zero digit are NOT significant
005.1 2 SF's
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Physics 10-5 || Ms. Teci Pulido 8
Scientific Notation
9.8765 x 104Example:
ONE significant figures
before decimal point
ALL OTHERsignificant figuresafter decimal point
Power of 10
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Physics 10-5 || Ms. Teci Pulido 9
Example
Express 3,428,579.610 using:
4 SF’s
2 SF’s
10 SF’s
3.429 x 106
3.4 x 106
3,428,579.610 or 3.428579610 x 106
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Physics 10-5 || Ms. Teci Pulido 10
Units of Measurement
● LENGTH
● TIME
● MASS
● TEMPERATURE
centimeter meter
inch
foot
millimeteryard
year second day
grampound
kilogram milligram
CelsiusFahrenheit
Kelvin
SI units
ounce
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Physics 10-5 || Ms. Teci Pulido 11
SI Units● “Système International”● Standard units for scientists and engineers● More convenient
Young and Freedman, Sears and Zemansky's University Physics with Modern Physics, 13th ed. (2012)
second meterkilogram
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Physics 10-5 || Ms. Teci Pulido 12
Some length scales :)
Young and Freedman, Sears and Zemansky's University Physics with Modern Physics, 13th ed. (2012)
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Physics 10-5 || Ms. Teci Pulido 13
Measurement:CONVERSION OF UNITS
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Physics 10-5 || Ms. Teci Pulido 14
Unit Relations1 year = 12 months = 365.25 days
1 meter = 100 centimeters = 1,000 millimeters
1 kilometer = 1,000 meters
1 yard = 3 feet
1 foot = 12 inches
1 kilogram = 1,000 grams
1 gram = 1,000 milligrams
* 1 inch = 2.54 centimeters* 1 kilogram = 2.2 poundsT
K = T
C + 273
TF = T
C*9/5 + 32
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Physics 10-5 || Ms. Teci Pulido 15
Unit Conversion
→ multiply by a fraction of equivalent relations.
Cancel units until you reach the desired unit.
Ex:
1 _____ seconds = 24 hours
2 _____ cm = 5.23 km
24 hours∗( 60minutes1 hour )∗( 60 seconds
1minute ) = 86,400 seconds
5.23km∗( 1000m1km )∗( 100cm
1m ) = 523,000 cm
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Physics 10-5 || Ms. Teci Pulido 16
Trivia!● The exact number of days in a
year is always changing!● The “weighing scale” actually
measures mass, not weight!● “Absolute zero” (0 K) is the point
where molecules have zero energy!
● A “pound” abbreviated as “lb”!
http://ujsciencelibrarian.pbworks.com/f/PHYSICS.jpg
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Physics 10-5 || Ms. Teci Pulido 17
Examples
1. Express 765,432.1000
a) using 10 SF's
b) using 6 SF's
2. Rewrite 5.321476 x 109 without using scientific notation
765,432.1000or 7.654321000 x 105
765,432. or 765,432 or 7.65432 x 105
5,321,476,000
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Physics 10-5 || Ms. Teci Pulido 18
Seatwork (Jan14)
1. 5.37 kg = _____ lbs
2. 84.9 lbs = _____ grams
3. (6 yrs + 3 mos) = _____ hrs
4. (5 ft 2 in) = _____ mm
5. 64 cm = _____ yards
Convert to the desired unit. Use at least 3 SF's for the final answer.
11.8
1,580
0.700
38,600
54,800
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Physics 10-5 || Ms. Teci Pulido 19
VECTORS
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Physics 10-5 || Ms. Teci Pulido 20
Vectors
– straight line segments that indicate magnitude and direction
This is a vector :)
Ex: VectorMagnitude: 7.0 cmDirection: East or 0°
V
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Physics 10-5 || Ms. Teci Pulido 21
Unit Vectors● Magnitude = 1 unit● Direction:
https://math-e-motion.wikispaces.com/
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Physics 10-5 || Ms. Teci Pulido 22
Describing two vectors
Parallel
(same direction)
Equal
(same magnitude, same direction)
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Physics 10-5 || Ms. Teci Pulido 23
“Equal” and “Opposite” Vectors
A
B
C
Example: Vectors A, B, C have same magnitudes (lengths)What about directions?
A = B
C =−B
A =−C
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Physics 10-5 || Ms. Teci Pulido 24
NO negative magnitudes
• Magnitude (Length) >= 0• The negative sign in a vector refers to direction
• – î: left• – ĵ: downward• : two antiparallel vectors
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Physics 10-5 || Ms. Teci Pulido 25
Vector Addition
● Computational
● Graphical– Tail-to-Tip
– Parallelogram
Add parallel components
Connect the tail of the next vector to the tip of the previous
Sum = Connect the first tail to the last tip
Draw parallelograms based on the x- and y-components Sum = the diagonal of the
resulting parallelogram
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Physics 10-5 || Ms. Teci Pulido 26
Vector Addition
Ex: Add: A = 5 î + 2 ĵ and B = - î + ĵ
Computational Method
Polygon /Tail-to-TipMethod
Parallelogram /Tail-to-Tail
Method
A + B
= (5 î + 2 ĵ) + (-î + ĵ)
A + B = 4 î + 3 ĵ
B
B
AAA+
BA+
B
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Physics 10-5 || Ms. Teci Pulido 27
Components of Vectors
= +Magnitude: Direction: Bet. x- and y-axes
Magnitude: Vx
Direction: Horizontal
Magnitude: Vy
Direction: Vertical
A vector can be expressed according to its
x- and y-components
V = V x i+V y j
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Physics 10-5 || Ms. Teci Pulido 28
Reviewing Trig :)
SOH-CAH-TOA:
sinθ = Opp/Hyp = Vy/V
cosθ = Adj/Hyp = Vx/V
tanθ = Opp/Adj = Vy/Vx
θ
V
V x
V y
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Physics 10-5 || Ms. Teci Pulido 29
ONE method (preferred by Ms. Teci)
• V, Vx and V
y form a right triangle
• θ counterclockwise from +x-axis
θ
V2 = Vx
2 + Vy
2
Vx = Vcosθ
Vy = Vsinθ
V
xV
yV
θ=tan−1(V y
V x)+θ '
θ' = 0º (Q1)θ' = 180º (Q2 or Q3)θ' = 360º (Q4)
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Physics 10-5 || Ms. Teci Pulido 30
Ex 1: Skaty PerryA skater travels 1 km North then 2 km West.
a) How far is he from the starting point?
b) In what direction is he going (based from the starting point)?
c) What are the magnitude and direction of the resultant displacement?
153.4°
Mag = 2.24 kmDir = 153.4°
5 = 2.24 km
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Physics 10-5 || Ms. Teci Pulido 31
Ex 2: Victor
Victor traveled 2.8 km, 30 degrees North of East. Find the components of his displacement.
N
S
W E
30°
• Angle (cc from +x-axis) = 30°• R
x = 2.8 cos 30° = 2.4 km
• Ry = 2.8 sin 30° = 1.4 km
* We can rewrite:
__= (2.4 km)(î) + (1.4 km)(ĵ)
http://adventuretime.wikia.com/wiki/File:75884-adventure-time.png
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Physics 10-5 || Ms. Teci Pulido 32
Ex 3: Vhector
http://adventuretime.wikia.com/wiki/File:75884-adventure-time.png
• Angle (cc from +x-axis) = 250°• R
x = 5.6 cos 250° = –1.9 yards
• Ry = 5.6 sin 250° = –5.3 yards
* We can rewrite:
= (–1.9 yards)(î) + (–5.3 yards)(ĵ)
Vhector wandered 5.6 yards, in the direction 20º W of S. Give the x- and y-components of this vector.
N
S
W E
20°5.6
yd
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Physics 10-5 || Ms. Teci Pulido 33
Ex 4: Princess VheckyVhecky went off on an adventure which took her 75 miles East and 35 miles South. What was her resultant distance and direction from her starting position?
http://adventuretime.wikia.com/wiki/File:Adventure_Time_Main_Line-Up.png
N
S
W E
θ?
75 mi
35 mi
• Vector: = (+75 mi)(î) + (–35 mi)(ĵ)• Magnitude:
• Direction: R ~ 83 mi
θ=tan−1(−3575 )+360
θ = 335º or 25º S of E or 65º E of S
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Physics 10-5 || Ms. Teci Pulido 34
SW (Jan 16) – part 11. Given the ff. forces:
= 5 N, N = 7 N, 30º N of W = 10 N, 75º W of S
Determine
F 1 F 2 F 3
W = F 3 + F 1 − F 2
F 1x = 5 cos90 = 0F 1y = 5 sin90 = 5
F 2x = 7 cos150 = −6.06F 2y = 7 sin150 = 3.5
F 3x = 10 cos195 =−9.66F 3y = 10 sin195 =−2.59
W = (−3.6 N ) i + (−1.09N ) j
(a) in component notation
(b) with magnitude and direction
W = −3.76 N ,197deg.
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Physics 10-5 || Ms. Teci Pulido 35
SW (Jan 16) – part 2
2. Given the ff. concurrent forces:
Give the resultant vector.
A = (−7.99 N ) i + (6.02 N ) j
B = (15N ) j
C =(14 N )(−k )
D = (−8 N ) i + (12 N ) j + (4N ) k
R = (−16 N ) i + (33N ) j − (10 N ) k
A = 10 N at 37deg. N of W
B = 15 N , North
C = 14N towards−z−axis
D = (−8 N ) i + (12 N ) j + (4N ) k
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Physics 10-5 || Ms. Teci Pulido 36
Reminders● Problem Set – next meeting (Jan 21)● Quiz # 1 – two meetings from today (Jan 23)
http://www.funnyjunk.com/channel/fucking-science/Physics+Student+Problems/tyGmGgl http://cdn.themetapicture.com/media/funny-mad-girl-student.jpg