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Phys 1111KSpring 2005

Course Overview

Dr. PereraRoom: 507 Science Annex

Phone: 651-2709, 3221/3222

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Introduction

• What is Physics ?

Understanding nature

• Laws of Physics

Wide spread impact on modern technology

• Every minute of your life is involved in Physics

Needs and Uses Even without knowing it

• A Fundamental Science Welcome to Introduction to

Physics

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Main Sections

Kinematics• Classical Mechanics (Chs 1-10)

both Transnational and Rotational Dynamics

• Fluid Mechanics (Ch 11)

• Thermodynamics (Chs 12-13)

Heat

Temperature

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Ch 1 Pre RequisitesCo-ordinate System (Cartesian)

•     Trigonometry

Pythagorean Theorem

Sin θ

Cos θ Pythagorean Theorem

Tan θ

•       Algebra

Quadratic Equations

Powers of 10

•      Symbols

Δx, μ, n, p

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Standards and Units

CGS British SI

Lengthcentimeter

(cm)foot (ft) meter (m)

Mass gram (g) slug (sl)kilogram

(kg)

Time second (s) second (s) second (s)

Why do we need standard units ?

King Louis

• Yard

• Royal foot

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SI Units

Le System International Units

• meter : Light travels in a vacuum in time of 1/ 299792458 seconds

• kilogram : Standard cylinder of Pl-Iridium alloy at room temperature

• second : Cs-133 atomic clock – time for 9192631770 wave cycles to occur

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Conversion of Units

1 meter = 100 centimeter = 1000 millimeter (mm)

103 meter = 1000 meters = 1 kilometer

0.001 meter = 10-3 meter = 1 millimeter

3.281 feet = 1 meter

5280 feet = 1 mile

3600 seconds = 1 hour

0.65 miles / hour = 95 feet / second = 29 meters / second

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Significant Figures

Keep the same number of significant figures in the answer as in the least accurate number

3.5 × 10.6 = 37 (not 37.1)

0 ± 0.1 0 ± 0.1 35 39

Uncertainty : Quality of the apparatus

Skill of the experimenter

Number of measurements

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Dimensional Analysis

•       Distance - [L]

•       Mass - [M]

•       Time - [T]

Check whether an equation is mathematically correct

Find an unknown exponent

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Vectors and Scalars

•       Addition and subtraction

•       Multiplying by a number

•      Components

• Vector addition by Components

• Vector addition by Graphing

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Vector Addition

(Due East) Resultant Displacement

R = A+ B

Due East and then Due north

R = A +B 5 = 4 +3 ? Find Theta

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What if Vectors are not Perpendicular ?

Can we say R = A +B ? But Pythagorean Theorem

valid ?

Graphical Technique

A = 275 m, B =125 m Scale 1 cm = 10 m

R = 228 m

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Vector Components

r = X + Y r A, X Ax Y AY

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Different Axes

Vector Components depend on the orientation of the axes

Scalar components

(With positive or negative sign)

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Adding Vectors Using Components

C = A +B, C = Cx + CY

A = Ax +Ay CX =

B = Bx + By CY =

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Example 8

A

B

R

x

y

A+B=R

A=Ax+Ay

B=Bx+By

Note By is in negative direction.

A

B

R

x

y

AX

Ay

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A

B

R

x

y

AX

Ay

20

BX

By

35

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Example 8 (continued)

x component y component

A Asin20=145sin20=49.6 Acos20=145cos20=136.3

B Bcos35=105cos35=86.0 -Bsin35=-105sin35=-60.2

R Ax+Bx=135.6 AY+BY=76.1

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Example 8 (continued)

)(tan 1

x

y

R

R )6.135

1.76(tan 1

m

m

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