Physics 10-4General Physics 1 – Lecture + Lab

http://www.desktopwallpapers4.me/digital-art/fire-vs-electricity-5402/

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

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! :)

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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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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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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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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Scientific Notation

9.8765 x 104Example:

ONE significant figures

before decimal point

ALL OTHERsignificant figuresafter decimal point

Power of 10

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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

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

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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Some length scales :)

Young and Freedman, Sears and Zemansky's University Physics with Modern Physics, 13th ed. (2012)

Physics 10-5 || Ms. Teci Pulido 13

Measurement:CONVERSION OF UNITS

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

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

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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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

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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VECTORS

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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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Unit Vectors● Magnitude = 1 unit● Direction:

https://math-e-motion.wikispaces.com/

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Describing two vectors

Parallel

(same direction)

Equal

(same magnitude, same direction)

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“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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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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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

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

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

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

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)

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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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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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

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

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.

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

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