Fundamental Physics: “Mechanics”, Slides of Physics

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Fundamental Physics:

“Mechanics”

Tuesday, 3 September 2019

Physics Department

FMIPA UNS

Introduction

 Fundamental Physics 1 – Course Information  Brief Introduction to Physics  Chapter 1 – Measurements (sect. 1-6)  Measuring things  Three basic units: Length, Mass, Time  SI units  Unit conversion  Dimension  Chapter 3 – Vectors (sect. 1-4)  Vectors and scalars  Describe vectors geometrically  Components of vectors  Unit vectors  Vectors addition and subtraction

Course Information: Grading

 Common Exams (17% each, 51% total)  Common Exam 1  Common Exam 2  Common Exam 3  Final Exam (29%)  Lecture/Recitation Quiz (8%)  Homework (12%)  Final Letter Grade A 85+ B+ 80- B 70- C+ 65- C 55- D 50- F < 50

Physics and Mechanics

 Physics deals with the nature and properties of matter and energy. Common language is mathematics. Physics is based on experimental observations and quantitative measurements.  The study of physics can be divided into six main areas:  Classical mechanics – Physics I  Electromagnetism – Physics II  Optics – Physics III  Relativity – Phys. 420  Thermodynamics – Phys. 430  Quantum mechanics – Phys. 442  Classical mechanics deals with the motion and equilibrium of material bodies and the action of forces.

Chapter 1 Measurement

 To be quantitative in Physics requires measurements  How tall is Ming Yao? How about his weight?  Height: 2.29 m (7 ft 6 in)  Weight: 141 kg (310 lb)

 Number + Unit

 “thickness is 10.” has no physical meaning  Both numbers and units necessary for any meaningful physical quantities

Type Quantities

 Many things can be measured: distance, speed,

energy, time, force ……

 These are related to one another: speed =

distance / time

 Choose three basic quantities (DIMENSIONS):

 LENGTH

 MASS

 TIME

 Define other units in terms of these.

Fundamental Quantities and SI Units Length (^) meter m Mass kilogram kg Time second s Electric Current ampere A Thermodynamic Temperature kelvin K Luminous Intensity candela cd Amount of Substance mole mol

Why should we care about units?

 Mars Climate Orbiter:

http://mars.jpl.nasa.gov/msp98/orbiter

 SEPTEMBER 23, 1999: Mars Climate Orbiter Believed To Be Lost  SEPTEMBER 24, 1999: Search For Orbiter Abandoned  SEPTEMBER 30, 1999:Likely Cause Of Orbiter Loss Found The peer review preliminary findings indicate that one team used English units (e.g., inches, feet and pounds) while the other used metric units for a key spacecraft operation.

SI Time Unit: Second

 1 Second is defined in terms of an “atomic clock”– time taken for 9,192,631,770 oscillations of the light emitted by a 133 Cs atom.  Defining units precisely is a science (important, for example, for GPS):  This clock will neither gain nor lose a second in 20 million years.

SI Mass Unit: Kilogram

 1 Kilogram – the mass of a specific platinum-iridium alloy kept at International Bureau of Weights and Measures near Paris. (Seeking more accurate measure: http://www.economist.com/news/leaders/21569417- kilogram-it-seems-no-longer-kilogram-paris-worth-mass)  Copies are kept in many other countries.  Yao Ming is 141 kg, equivalent to weight of 141 pieces of the alloy cylinder.

Prefixes for SI Units

x

Prefix Symbol

x=18 exa E

15 peta P

12 tera T

9 giga G

6 mega M

3 kilo k

2 hecto h

1 deca da

 3,000 m = 3  1,000 m = 3  10 3 m = 3 km  1,000,000,000 = 10 9 = 1G  1,000,000 = 10 6 = 1M  1,000 = 10 3 = 1k  141 kg =? g  1 GB =? Byte =? MB If you are rusty with scientific notation, see appendix B.1 of the text

x

Prefix Symbol

x=-1 deci d

-2 centi c

-3 milli m

-6 micro μ

-9 nano n

-12 pico p

-15 femto f

-18 atto a

Prefixes for SI Units

 0.003 s = 3  0.001 s = 3  10

• s = 3 ms  0.01 = 10

= centi  0.001 = 10

= milli  0.000 001 = 10

= micro  0.000 000 001 = 10

= nano  0.000 000 000 001 = 10

= pico = p  1 nm =? m =? cm  3 cm =? m =? mm

Other Unit System

 U.S. customary system: foot, slug, second  Cgs system: cm, gram, second  We will use SI units in this course, but it is useful to know conversions between systems.  1 mile = 1609 m = 1.609 km 1 ft = 0.3048 m = 30.48 cm  1 m = 39.37 in. = 3.281 ft 1 in. = 0.0254 m = 2.54 cm  1 lb = 0.465 kg 1 oz = 28.35 g 1 slug = 14.59 kg  1 day = 24 hours = 24 * 60 minutes = 24 * 60 * 60 seconds  More can be found in Appendices A & D in your textbook.

Unit Conversion

 Example: Is he speeding?  On the garden state parkway of New Jersey, a car is traveling at a speed of 38.0 m/s. Is the driver exceeding the speed limit?  Since the speed limit is in miles/hour (mph), we need to convert the units of m/s to mph. Take it in two steps.  Step 1: Convert m to miles. Since 1 mile = 1609 m, we have two possible conversion factors, 1 mile/1609 m = 6.215x10-^4 mile/m, or 1609 m/1 mile = 1609 m/mile. What are the units of these conversion factors?  Since we want to convert m to mile, we want the m units to cancel => multiply by first factor:  Step 2: Convert s to hours. Since 1 hr = 3600 s, again we could have 1 hr/3600 s = 2.778x

• 4 hr/s, or 3600 s/hr.  Since we want to convert s to hr, we want the s units to cancel => m 1mile 38.0 mile 2 38.0 2.36 10 mile/s s 1609 m 1609 s   ^  -  ^ ^ ^ ^ ^    (^)   This image cannot currently be displayed. 2 mile^ 3600 s 38.0 m/s 2.36 10 85.0 mile/hr = 85.0 mph s hr

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