unit 1: introduction to physics...jan 06, 2016 · unit 1: introduction to physics review of prior...

UNIT 1: INTRODUCTION TO PHYSICS

WED-1/6/2016

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UNIT 1: INTRODUCTION TO PHYSICS

Review of prior learners background of math and science

1. Class Activity 1/6/16: Background in Science

1. List any three areas that you have learned in science (mathematics, chemistry, physical science, computer science)?

2. Expand your list by including the answers stated by your class members.

2. Class Activity 2/6/16: Background in mathematics

1. List any field, formula etc that you have learned in branch of mathematics since grade 1? Include the formula if you can?

2. Expand your list by including the answers mentioned by your class members

3. Homework Assignment Due 1/8/2016:

– Definition of Physics; Branches of Physics; Why we care about physics (importance of studying physics i.e ); relation between physics and other subjects; jobs or occupations in physics 2

ASSIGNMENTS: DUE FRIDAY 1/8/2016

• Research Assignment:( state your source i.e. the name of the book or website that you used to get answers for the following questions)

1. Define Physics ( 3-definations).

2. List branches of physics ( you are not required to but can explain if you want )

3. State at least three relation between physics and other sciences.

4. State three reasons why we care about physics (i.eimportance of studying physics or how physics might help you in future)

5. List any occupations/job in physics

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Introduction to Scientific Methods:

• Working as a group of two , estimate the surface are and volume of the top of your classroom table.

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Scientific Method: Predict and Investigate Area and Volume of your table top?

Source: diagram from www.makeitsolar.com

Scientific Method: Simple experiment (Predict and Investigate Area and Volume of your table top)

Activity 1/7/16 to1/8/16 t: Show the following:1. Topic: (Example: Investigating(Finding or Estimationg) the Surface Area and

Volume of the Table top)

2. Identify Question/Problem/Goal/Objective

3. Research the problem

4. Predictions (hypothesis or tentative answers)

5. Design or write the procedure or steps that you would use to perform the experiment

6. Do the investigation and collect data to test your predictions (hypothesis). (Show your recorded data (Length, width and Height)

7. Data Analysis and Calculations ( Show formula and step by step calculations of Area and Volume. Show your e)

8. Formulate Conclusion: Do your answers agree with your predictions? Why or why not.

No measurement is perfect. Why do you think may not be 100% correct to the actual value (i.egive possible sources of error in your measurements).

Report your results: Compare your answers with those of your neighbors. Why do you think your answers and their answers are not the same.

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MEASUREMENTS

In this section , we shall learn the following: Measurements of Physical Quantities

1. Physics quantities

2. 7 Base Quantities

3. Dimension of Physical quantities

4. Units of Measurements

5. Conversion of Units from one for to another

6. Unit of physical physical quanties

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The Most Basic Measurements Base Quantities

• Base Quantities are physical measurements that define a standard quantity.

• Often base quintiles can not be simplified into a simpler set of quantities

• Seven (7) Base Measurements

• 1. length (L) 5. amount of substance (mole)

• 2. time (t) 6. electric current (I)

• 3. mass (m) 7. luminous intensity (candela)

• 4. temperature (Kelvin)

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Derived Quantities

• Derived Quantities are physical measurements using combinations of base quantities.

• Examples:

1. Speed or velocity (v); length/time (L/t)

2. Area (A); length x length (L2)

3. Volume (V); length x length x length (L3)

4. Acceleration (a); Δvelocity/time (L/t/t) (L/t2 )

5. Force (F); mass x acceleration (m∙ L/t2)

6. work & energy (joule)(J); force x distance (F∙L)

7. many many more 9

Standard Units of Measurement

• Two widely accepted standard units of measurement

1) BRITISH system : only used by 1 major industrialized country USA)

2) METRIC system (SI system): used by the rest of the industrialized world and Physists

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Systseme International (SI)

• Systseme International (SI) is the metric system, it has its origins in the late 1700’s

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• UNITS of MEASUREMENT for SI

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• Base Quantities Standard SI Units• length meter

• time second

• mass kilogram ≠ weight

• electric current ampere

• temperature Kelvin

• amount of a substance mole

• luminous intensity candela

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• time second


• These three quantities are the units most often used in the 1st

semester of this course

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Systseme International (SI) MKS




• time second


• This is the MKS measurement system of the SI

meter kilogram second are the standards for basic measurement

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Systseme International (SI) MKS




• time second


• This is the MKS measurement system of the SI

meter kilogram second are the standards for basic measurement

• We will be using the MKS measurements in this course

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Systseme International (SI) cgs

• Base Quantities Standard SI Units Abbreviation

• Length centimeter cm

• time second s

• mass grams ≠ weight g

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Systseme International (SI) cgs

• Base Quantities Standard SI Units Abbreviation

• length centimeter cm

• time second s

• mass grams ≠ weight g

• This is the cgs measurement system of the SI

Centimeter gram second are the standards for basic measurement

• We will NOT be using cgs measurements in this course

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Value of SI measurements

length (meter) 1/10,000,000 distance from equator to North Pole along a meridian line running through ParisDistance traveled in 1/ 299,792,458 of a second by light in a vacuum

Mass (kilogram) 1/1,000 of a cubic of pure water at 4oCmass of a particular platinum- iridium cylinder kept at the International Bureau of Weights and Measurements in Paris

Time (second) 1/86,400 of a mean solar day9,192,631,770 periods of radiation released from cesium atoms

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Value of SI measurements

Other measurements will be introduced as needed

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Prefixes; Measurement Modifiers

• In the British system different measurements of the same base quantity have different names

length: feet, inches, yards, miles, etc

weight: pounds, ounces, tons

time: seconds, minutes, hours, days, years, etc

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• In the SI system prefixes combined with a common root are used to express different quantities

length: meter, kilometer, centimeter, millimeter

mass: gram, milligram, kilogram, decagram,

time: second, millisecond, kilosecond, megasecond

hours, minutes, years

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standard base units in SI system

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• NOTICE THAT THE STANDARD BASE UNIT FOR MASS IN THE METRIC SYSTEM IS A

KILOGRAM24


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Conversion Factors

• Often times a measured quantity in one set of units must be converted to an equivalent quantity in another set of units

• To make the conversion, a conversion factor is required.

• A conversion factor is often expressed as a fraction with the numerator and denominator having the same quantity expressed in different units

• The quantity to be converted is then multiplied by the conversion factor. The units to be changed must cancel leaving only the desired unit(s).

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Examples of Conversion Factors

• 12 inches/1 foot

• 1 foot/12 inches

• 36 inches/ 1 yard

• 1 yard/ 36 inches

• 60 seconds / 1 minute

• 1 minute/ 60 seconds

• 3600 seconds/ 1 hour

• 2.54 cm/1 inch

• 1000m/kilometer 1000m/km

• 1 m/1000mm

In each example the quantity in the numerator equals the quantity in the denominator

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A conversion factor

must have a value of

1 (one).

Applicatin of Conversion Factors

1. Convert 18 inches into feet

18 inches (1 foot/12 inches) = 1.5 feet

2. Convert 1.33 hrs into seconds

1.33 hrs (3600 seconds/1 hr) = 4788 seconds

sig figs 4790 seconds

3. Convert 758 mm into meters

758 mm (1 m/1000mm) = 0.758 m

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Application of Conversion Factors

Sometimes two or more conversion factors must be used.

4. Convert 26.7 m/s into kilometers/hr

26.7 m/s ( 1 km/1000m) ( 3600 s/1 hr) = 96.12 km/hr

sig figs 96.1 km/hr

5. Convert 4580 cm3 into m3

4580 cm3 (1 m/1000cm)3 = 0.000004580 m3

= 4.58 x 10-6 m3

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Conversion Factorsproper dimension

• When using conversion factors the original measurement must have the same dimension as the final measurement

• 60 km/minute (1 minute/60 sec) = 1 km/sec

• velocity dimension = velocity dimension

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Dimensional Analysis

Dimensional analysis: is a procedure that determines if a mathematical equation will produce the expected dimension.

•If the equation is expected to produce the dimension length, each number in the equation should be a length

• 6m + 4m = 10 m

• L + L = L

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•6m + 6ft = ?

• L + L = L

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•6m + 6ft = ?

• L + L = L

• dimensionally correct

• 3m/s(5s) + 6m = 21m

• L + L = L

• dimensionally correct

• 35m + 15 s = 50m

• L + t ≠ L

• dimensionally incorrect33


• To be mathematically correct an equation must be dimensionally correct

• An equation that is dimensionally correct may not be mathematically correct

• This will be demonstrated and explained further at a later time

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Unit Analysis

In an equation, measurements will involve units of time, length, mass, velocity, force etc.

Unit analysis is analyzing each of these measurements to be sure that each measurement is using the same unit

5 min + 10 min = 15 min

units are correct-- same time unit thru out the equation

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Unit Analysis

5 min + 600 sec = ?

Seconds can not be added to minutes

•Dimensionally correct

• Units of time are not the same

•Equation can not be solved in this form

•Requires a conversion

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Unit Analysis

5 min + 600 sec = ?

•5 min ( 60 sec/min) = 300 sec

300 sec + 600 sec = 900 sec

•Dimensionally correct

• Units of time are the same

•Equation can be solved in this form

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• Order of magnitude could also be considered a type of measurement

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unit 1: introduction to physics...jan 06, 2016 · unit 1: introduction to physics review of prior...

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