adv ch.1 measuring and units final-0

7/28/2019 Adv Ch.1 Measuring and Units Final-0

1/28

The Science of Physics Section 1

UNIT OUTLINE--TOPICS

What is Physics?

Branches of Science

Science Terms

Scientific models

Measuring and Units

Powers of Ten and conversions

Graphing

Experimental Design Science vs. Technology

Analyzing in Physics


2/28

The Science of Physics Section 1Chapter1

OBJECTIVES

List basic SI units and the quantities they describe.

Using prefixes and powers of ten.

Distinguish between accuracy and precision.

Taking good measurements

Use significant figures in measurements and

calculations.


3/28


INTERNATIONAL SYSTEM OF UNITS (SI

UNITS)

Developed for the sake of

consistency

ease of understanding

sharing data


4/28


BASE SI UNITS (STANDARD UNITS)

Measured quantity


5/28


DERIVED UNITS

Derived Units: Combinations of the 7 base units.

Examples

Area (length x width) m x m = m2

Velocity (distance/time) = m/s

10 meters

5 meters50 m2


6/28



7/28


NUMBERS AS MEASUREMENTS

In SI, the standard measurement system for science,

there are seven base units.

Each base unit describes a single dimension, such

as length, mass, or time.

The units of length, mass, and time are the meter

(m), kilogram (kg), and second (s), respectively.

Derived units are formed by combining the seven

base units with multiplication or division. Forexample, speeds are typically expressed in units of

meters per second (m/s).


8/28


MEASUREMENTS

Measurements consist

of a number and a unit. Example

100 meters

the number of

units or valuethe unit


9/28


DIMENSIONS AND UNITS

Measurements of physical quantities must be

expressed in units that match the dimensions of that

quantity.

In addition to having the correct dimension,measurements used in calculations should also

have the same units.

For example, when

determining area by

multiplying length and width,

be sure the measurements

are expressed in the same

units.


10/28


OBJECTIVES






11/28

The Science of Physics Section 2Section 2 Measurements inExperimentsChapter1

SI PREFIXES

In SI, units arecombined withprefixes thatsymbolize

certain powersof 10. The mostcommonprefixes andtheir symbolsare shown in the

table.


12/28


OBJECTIVES






13/28

The Science of Physics Section 2Section 2 Measurements inExperimentsChapter1

Accuracy and Precision

Accuracy is a description of how close ameasurement is to the correct or accepted valueof the quantity measured.

Precision is the degree of exactness of ameasurement.

A numeric measure of confidence in a

measurement or result is known as uncertainty. Alower uncertainty indicates greater confidence.


14/28


ACCURACY

Accuracy is the extent

to which a

measurement

approaches the truevalue.

Your Time:

2:05 pm

Actual Time:

2:10 pm

Your accuracy is off by 5minutes


15/28


ACCURACY AND PRECISION

Precision is the degree

of exactness for a

measurement.

It is a property of theinstrument used.

The length of the pencilcan be estimated totenths of centimeters.

Accuracy is how close

the measurement is to

the correct value.


16/28


ERRORS IN MEASUREMENT Instrument error

Instrument error is caused by using measurementinstruments that are flawed in some way.

Instruments generally have stated accuracies such asaccurate to within 1%.

Method error Method error is caused by poor techniques (see picture

below).


17/28


- THE BULLS EYE REPRESENTS THE TRUE VALUE.- THE DARTS REPRESENT THREE SEPARATE MEASUREMENTS

accurate

less accurate

these darts

show good

accuracy

which paint ball

mark is more

accurate?


18/28


PRECISION

Precision is the degree

of exactness of a

measurement.

Based on the scale of

the measuring

instrument.

Smallest tick marksrepresent millimeters

(mm)


19/28


PRECISION VS. ACCURACY

AGood precision and

accuracy

BSome accuracy

and poor precision

CGood precision and

poor accuracy

DPoor precision and

accuracy

A B C D


20/28


DISCUSSION QUESTION When shooting free throws, is it better to be precise

or accurate?


21/28


Its better to be accurate.


22/28


OBJECTIVES






23/28


MEASUREMENTS

Dimension - the kind of physical quantity being

measured

Examples: length, mass, time, volume, and so on

Each dimension is measured in specific units. meters, kilograms, seconds, liters, and so on

Derived units are combinations of other units.

m/s, kg/m3, and many others

Scientists use the SI system of measurement.


24/28


HOW TO MEASURE?

Know how to operate the measuring instrument

Which unit(s) is represented?

What does each tick mark represent?

Are there multiple scales? Did you zero out the instrument (if possible)

Be skilled and patient enough to measure with the

greatest detail possible


25/28


WHAT DO THE TICK MARKS REPRESENT

ON A METER STICK? What unit is represented by the smallest tick mark

on the meter stick?

m?

dm?

cm?

mm? *


26/28


WHAT DO THE TICK MARKS REPRESENT

ON A METER STICK? What is the measurement?

In mm?

65 mm

In cm?

6.5 cm

In dm?

.65 dm

In m?

0.065 m?


27/28


WHY SO MANY DIFFERENT UNITS OF MEASUREMENT FOR THESAME QUANTITY?

Consider Mark and Suzy. They want tomeasure the length of a room.

The quantity they are measuring is distance

(measured quantity). They both measure length in units of feet

(the length of one foot) This is theirmeasuring units.

One important detail: Marks foot is longer

than Suzys foot.


28/28


WHY SO MANY DIFFERENT UNITS OF MEASUREMENT FOR THESAME QUANTITY?

Mark measures the length of the room. So doesSuzy. Will they have the same measurement? Whyor why not? Who will have the longer measurementin feet?

Marks measurement is 18 feet and Suzys is 23 feet. The length of a markfoot is not the same as the

length of a suzyfoot.

To compare the two different measurements, oneunit must be converted into the other so that both

measurements are proportional. Standardizing units means to select either the length

of Marks or Suzys foot as the accepted length ofthe unit called a foot.

adv ch.1 measuring and units final-0

Documents