f1 ppt units and measurements

8/12/2019 F1 Ppt Units and Measurements

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Units

andMeasurement

PhysicsMrs. Coyle

International Space Stationhttp://apod.nasa.gov/apod/image/0706/iss_sts117_big.jpg


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It All Starts with a Ruler!!!


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Math and Units Math- the language of Physics SI Units International System

MKS Meter m Mass kg Time s

National Bureau of Standards

Prefixes


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SI Unit Prefixes - Part I

Name Symbol Factortera- T 10 12

giga- G 109

mega- M 10 6

kilo- k 103

hecto- h 10 2

deka- da 10 1


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SI Unit Prefixes- Part II

Name Symbol Factordeci- d 10 -1

centi- c 10 -2

milli- m 10 -3

micro- 10 -6

nano- n 10 -9

pico- p 10 -12

femto- f 10-15


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The Seven Base SI UnitsQuantity Unit Symbol

Length meter mMass kilogram kg

Temperature kelvin KTime second s

Amount ofSubstance

mole mol

Luminous Intensity candela cd

Electric Current ampere a


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Derived SI Units (examples)Quantity unit Symbol

Volume cubic meter m 3

Density kilograms percubic meter

kg/m 3

Speed meter per second m/s

Newton kg m/ s 2 NEnergy Joule (kg m 2/s 2) J

Pressure Pascal (kg/(ms2

) Pa


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SI Unit Prefixes for LengthName Symbol Analogygigameter Gm 10 9

megameter Mm 10 6

kilometer km 103

decimeter dm 10 -1

centimeter cm 10 -2

millimeter mm 10 -3micrometer m 10 -6

nanometer nm 10 -9

picometer pm 10 -12


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Scientific Notation

M x 10 n

M is the coefficient 1


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Other Examples:

5.45E+6 or

5.45 x 10^6


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Numbers less than 1 will have anegative exponent.

A millionth of a second is:

0.000001 sec 1x10 -61.0E-6 1.0^-6


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Factor-Label Method of UnitConversion

Example: Convert 5km to m: Multiply the original measurement by a

conversion factor.

NEW UNIT85 km x 1,000 m = 85,000m

1km

OLD UNIT


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Factor-Label Method of UnitConversion: Example

Example: Convert 789m to km:

789m x 1km =0.789km= 7.89x10 -1km1000m


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Convert 75.00 km/h to m/s

75.00 km x 1000 m x 1 h___ = 20.83m/sh 1 km 3600 s


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Limits of Measurement

Accuracy and Precision


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Accuracy - a measure of howclose a measurement is to thetrue value of the quantity being

measured.


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Example: Accuracy

Who is more accurate whenmeasuring a book that has a truelength of 17.0cm?

Susan :17.0cm, 16.0cm, 18.0cm, 15.0cm

Amy:15.5cm, 15.0cm, 15.2cm, 15.3cm


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Precision

a measure of howclose a series of measurements

are to one another. A measure of

how exact a measurement is.


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Example: Precision

Who is more precise when measuringthe same 17.0cm book?

Susan :17.0cm, 16.0cm, 18.0cm, 15.0cm

Amy:

15.5cm, 15.0cm, 15.2cm, 15.3cm


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Example: Evaluate whether thefollowing are precise , accurate or

both .

Accurate

Not Precise

Not Accurate

Precise

Accurate

Precise


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Significant Figures

The significant figures in ameasurement include all of the

digits that are known, plus onelast digit that is estimated.


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Centimeters and Millimeters


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Finding the Number of Sig Figs:

When the decimal is present, start countingfrom the left.

When the decimal is absent, start countingfrom the right.

Zeroes encountered before a non zero digitdo not count.


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How many sig figs?

100 10302.00

0.001

10302 1.0302x10 4


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Sig Figs in Addition/Subtraction

Express the result with the samenumber of decimal places as thenumber in the operation with the leastdecimal places.Ex: 2.33 cm

+ 3.0 cm5.3 cm

(Result is rounded to one decimal place)


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Sig Figs in Multiplication/Division

Express the answer with the same sigfigs as the factor with the least sig

figs. Ex: 3.22 cm

x 2.0 cm

6.4 cm 2(Result is rounded to two sig figs)


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Counting Numbers

Counting numbers have infinite sigfigs.

Ex: 3 apples


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Solving Word Problems

Analyze List knowns and unknowns. Draw a diagram. Devise a plan. Write the math equation to be used.

Calculate If needed, rearrange the equation to solve for the

unknown. Substitute the knowns with units in the equation and

express the answer with units. Evaluate

Is the answer reasonable?

f1 ppt units and measurements

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