PHYSICS

V. HASSELL

Physics

is the science that studies

the nature of matter,

energy and their

relationships.

STATE THE 5 BASE QUANTITIES AND THEIR SI UNIT

METRIC SYSTEMSI unit of timesecondbased on atomic standardradiation emitted by cesium 133

METRIC SYSTEMSI unit of lengthmeterwavelength of light emitted by

krypton-86distance light travels in 1/2999

792 458 second

METRIC SYSTEMSI unit of masskilogramthe quantity of matter an object

containsmass of a platinum-iridium

metal cylinder kept near Paris

STANDARD UNITSKiloHectoDekagram- meter- literdecicentimilli

PREFIXES- FRACTIONS

deci d 1/10 or 10 -1centi c 1/100 or 10 -2milli m 1/1000 or 10 -3 micro u 10 -6nano n 10 -9pico p 10 -12

PREFIXES- MULTIPLES

Deka da 10 1

Hecto h 10 2

Kilo k 10 3

Mega M 10 6

Giga G 10 9

mass- kg

length-

meter

time- second

are combinations

of fundamental

quantities

density=

mass/volume

Fundamental quantities & units

Derived quantities

SIGNIFICANT DIGITS

Nonzero digits are

always significantAll final zeros after

the decimal point

are significant

Significant digits are

all the digits of a

measurement that

are certain plus one

estimated digit.

Your answers cannot be more precise than the least precise quantity.

The sum or difference of two values is as precise as the least precise value.

Zeros between two

other significant digits

are always significant

Zeros used solely for

spacing the decimal

point are not

significant

In scientific notation all

digits before the 10 are

significant

2.510 X 10 8 has

______ significant digits

SIGNIFICANT DIGITS- X OR /

The result of any

mathematical

operation with

measurements can

never be more precise

than the least precise

measurement.

Note the factor with

the least number of

significant digits.

Round the product or

quotient to this

number of digits.

SCIENTIFIC NOTATION

M X 10n

only 1 non-zero digit on the left of the decimal

the exponent gets larger as the number gets smaller

850 METERS = ___________MM

smaller unit - the # gets larger

larger unit - the # gets smaller

number of places- deci, centi, milli

move 3 times- larger number

*smallest units will have largest

numbers

CONVERSION

850 meters = ___________mm

850,000 mmor 8.5 X 10 5 mm

OR CONVERSION850 meters = ___________mm

1 meter = 1 X 1000 mm850 meters 1 X 1000 mm =

1 meter 850,000 mm or 8.5 X 10 5 mm

OR CONVERSION

850 meters = ___________mm

1 meter = 1 X 10 3 mm850 meters 1 X 10 3 mm =

1 meter

850 X 10 3 = 8.5 X 10 5 mm

ADD & SUBTRACT EXPONENTS

the exponents must be the same

Add the numbers in front of the 10

ADD & SUBTRACT EXPONENTS

2.1 X 10 3 + 3.2 X 10 3 =

2.1+ 3.2= 5.35.3 X 10 3

ADD & SUBTRACT EXPONENTS

3.2 X 10 3 - 2.1 X 10 3 =

3.2-2.1 = 1.11.1 X 10 3

ADD & SUBTRACT W/DIFFERENT EXPONENTS

Exponents must be the same number

(doesn’t matter which one)

Change one of them to match the

other (or in between)

Continue to add or subtract # before

10

ADD & SUBTRACT DIFFERENT EXPONENTS

5.5 X 10 -2 + 2.2 X 10 -3 =

55 X 10 -3 + 2.2 X 10 -3 =

57.2 X 10 -3=

5.7 X 10-2

SUBTRACT

5.5 X 10 -2 - 2.2 X 10 -3 =

55 X 10 -3 - 2.2 X 10 -3 =

52.8 X 10 -3 =

5.28 X 10 -2

5.3 X 10 -2

MULTIPLY & DIVIDE

Multiply or divide the # before

10 as indicated

add exponents in multiplication

subtract exponents in division

check units. (May be m2 or

m/sec)

MULIPLY

5.0 X 10 -2m X 3.0 X 10 -3m =

15.0 X 10 -2 + -3 m2=

15.0 X 10 -5 =

1.5 X 10 -4 m2

DIVIDE

6.6 X 10 -2m / 3.3 X 10 -5s =

2.0 X 10 -2 - (-5) m/s =

10 -2+ 5= 10 3

2.0 X 10 3m/s =

2.0 X 10 2m X 3.3 X 10 -5kg 6 X 10 -5s =

=6.6 X 10 2 + (-5)= -3 mkg = 6 X 10 -5s

1.1 X 10 -3 -(-5)= -3+5=2

1.1 X 10 2 mkg/s

All measurements are subject of uncertainties

All instruments

are subject to

external

influences.

Uncertainties in

measurement

cannot be

avoided.

INACCURACIES CAN BE DUE TO

human error

in reading

(precision)

accuracy of

the devise

PARALLAXThe apparent

shift in the

position of an

object when it

is viewed from

various angles

==WHAT IS ERROR?==

Error is the

difference between

the actual value of a

quantity and the

value obtained in

measurement.

Systematic errors are errors which tend to shift all measurements in asystematic way so their mean value is displaced. Systematic errors can be compensated if the errors are known.

SOURCES OF SYSTEMATIC ERROR

zero error, which cause by an

incorrect position of the zero point

an incorrect calibration of the

measuring instrument.

consistently improper use of

equipment.

PRECISION

The precision of a

measurement

describes how

exactly it was

measured

the ability of an

instrument in measuring

a quantity in a

consistent manner with

only a small relative

deviation between

readings

WHAT IS MEANT BY SENSITIVITY OF A MEASURING INSTRUMENT?==

The precision of

an instrument

is limited by

the smallest

division on the

measurement

scale

Measuring instruments that have

smaller scale parts are more

sensitive.

Sensitive instruments need not

necessarily be accurate.

MICROMETER SCREW GAUGE

Turn the thimble until the

object is gripped gently

between the anvil and

spindle.

Turn the ratchet knob until

a "click" sound is heard.

This is to prevent exerting

too much pressure on the

object measured.

Take the reading.

MICROMETER SCREW GAUGE

Reading of main scale = 5.5mm

Reading of thimble scale = 0.27mm

Actual Reading = 5.5mm + 0.27mm = 5.77mm

ACCURACY

Accuracy of a

measurement

describes how

well the result

agrees with a

standard value

The accuracy of a

measurement is

the approximation

of the

measurement to

the actual value

for a certain

quantity

STEPS TO REDUCE SYSTEMATIC ERROR

Conducting the experiment with care.

Repeating the experiment by using

different instruments.

RANDOM ERROR

Random errors

arise from unknown

and unpredictable

variations in

condition.

It changes from

one measurement

to the next.

Random error can cause

by:lack of sensitivity of the

instrument: the instrument

fail to respond to the small

change.

natural errors such as

changes in temperature or

wind, while the experiment

is in progress.

wrong technique of

measurement.

HOW TO AVOID RANDOM ERROR

Taking repeat readings

Find the average value of the

reading.

ZERO ERROR

A zero error arises when the measuring

instrument does not start from exactly

zero.

Zero errors are consistently present in

every reading of a measurement.

The zero error can be positive or

negative.

HOW TO MEASURE THE PRECISION OF A MEASUREMENT?==

The precision of a reading can be

indicated by its relative deviation.

The relative deviation is the percentage

of mean deviation for a set of

measurements and it is defined by the

following formula:

REVIEW

Accuracy is determined by the

preciseness of the

measurement

To check the accuracy of an

instrument you measure a

standard devise to determine

the deviation.

ACCURACY

The accuracy of an instrument is usually off the

same direction in all measurements.

Ex.

A scale which indicates a measurement over 0

with nothing being balanced will probably show

a higher than accurate amount for all

measurements.

MURPHY’S LAW

Any error that can creep in,

it will. It will be in the

direction that will do most

damage to the calculation.

Never mix units. For example does 30 pounds added to 20 newtons equal 50? NO

If the forces do not act along a straight line you can use the Graphical method to find the resultant sum.

Also, you can use the Pythagorean theorem to find the resultant sum.

The Pythagorean theorem is

A2 + B2 = C2

If A = 40 N and B equals 30 N, what is the resultant sum (C)?

1. A2 + B2 = C2

2. A=40; B=30 402 + 302 = C2

3. 1600 + 900 = C2

4. 2500 = C2

5. 50 = C

First plug in what you know Square A and B Add A and B Square root the answer