introduction to physics1

8/7/2019 introduction to physics1

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1.11.1

UNDERSTANDING PHYSICSUNDERSTANDING PHYSICS


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What is physics?What is physics?

y Physics is a branch of science whichstudies physicalandnatural phenomenaaroundus.

y Observe the followingthings :x Lightning

x Tsunami

x Mobile phones

x Emails


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CAREERS INPHYSICS

Engineering

Research

Education

Industry Medicine

Mechanical

Electrical

Computer

Environmental engineers

Scientist

Professor

astronaut

Lecturer

Teacher

Education officer

Radiologist

Forensic expert

technician

Medical physician

Geophysician

Quality control engineer


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1.21.2

Understanding Base Quantities andUnderstanding Base Quantities and

Derived QuantitiesDerived Quantities


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Physical quantities Non-physical

quantities

A quantity that is measurable Quantities which cannot be

measured

Based quantities andderivedquantities

-

Examples:

Mass, time, temperature.

Examples:

Beauty, feeling.

Length, l = 20 m -

Physical

quantities

Numerical

value

unit


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Base QuantitiesBase Quantities

y Base quantities are physical quantities that

cannot be defined interms of other

quantities.

y Five base quantities

1. Length

2. Mass

3. Time

4. Electric current

5. temperature


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Base quantities and SI unitsBase quantities and SI units

Base quantity SI units

Name Symbol Name Symbol

Length l Metre m

Mass m Kilogram kg

Time t Second s

Electric current I Ampere A

Temperature T Kelvin K


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Derived QuantitiesDerived Quantities

y physical quantities derived by combining

base quantities through multiplication or

division or both


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Derived quantities andunitsDerived quantities andunits

Derived

quantity

Symbol Formula Derived units

Area A Length x breadth m2

Volume V Length x breadth x height m3

Velocity v Displacement

Time

m s-1

Acceleration a Velocity

Time

m s-2

Force F Mass x Acceleration kg m s-2

Density V Mass

Volume

kg m-3


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Scientific notation / standard formScientific notation / standard form

y Is used for expressing verylarge and very

smallnumbers

y General form :-

x Where 1 eA < 10 and N is a positive/negative

integer

y Example:-1. 0.00000051m = 5.1 x 10-7 m

2. 3000000 m s-1 = 3.0 x 106 m s-1

A x 10 N


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PrefixPrefix

y Prefixes are usedto represent physical

quantities whichare very big or very

small in SI unit.

y Example:x 2000m can be writtenas 2.0 km

x 3cm can be writtenas 0.03m or 3x10-2 m


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Prefix Factor Symbol

Tera 1012 T

Giga 109

GMega 106 M

Kilo 103 k

Hecto 102 h

Deca 10 da

Deci 10-1 d

Centi 10-2 c

Milli 10-3 m

Micro 10-6 Q

Nano 10-9 n

Pico 10-12 p


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Conversion ofunitsConversion ofunits

Prefix Base units

X factor

factor


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CONVERSI

ONO

FCO

NVERSIO

NO

FUNITSUNITS


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Example 1Example 1

y convert512 000 gto kilogram (kg)and

write answer in standard form

Solution:

1 kg = 1x103 g 1g = 1x10-3 kg

512 000 g = 512 000 x 10-3 kg

= 512 kg

Standard form 5.12 x 102 kg


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Example 3Example 3

y 1.05g cm-3 = __________ kg m-3

Solution:

1kg = 1x103 g 1g = 1x10-3 kg

1cm = 1x10-2 m 1cm-3 = 1x106 m-3

1.05g cm-3 =1.05 x 10-3 kg x 106 m-3

= 1.05 x 103 kg m-3


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Example 4Example 4y 20 km h-1 = ___________m s-1

Solution:

1km = 1x103

m1h = 3600s

20 km h-1 =

= = 0.0056 x 103 m s-1

Standard form 5.6 m s-1

h

km20

s3600

m1020 3v


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Exercise 1Exercise 1

y Express the following measurement inthe

unit specified

1. 15 m s-1 = _____________ km h-1

2. 643 mg = ___________kg

3. 3.86 Ms = ___________ds

4. 6.37 km = ___________Qm

5. 40 cm2 = ____________ m2


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Exercise 2Exercise 2

y Identifythe smallestandthe largest

measurements from the following

nm10x2.42

km10x2.42

m10x2.42

cm10x2.42

8

3

10

-2


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1.31.3

Understanding scalar and vectorUnderstanding scalar and vector

quantitiesquantities


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Scalar and vector quantitiesScalar and vector quantities

Scalar quantities Vector quantities

a physical quantity whichhas

onlymagnitude

a physical quantity whichhas

bothmagnitude anddirection

examples:

length, speed, time, density,

temperature

examples:

force, acceleration, velocity

adding scalar usingsimple

addition

adding vector using

graphical method


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Example 1Example 1

An object is displaced 8 m to the east followed byanother

displacement of 10 m northwest.What is totaldistance

andthe displacement ofthe object?

WE

N

S


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Example 2Example 2

y Which ofthe following is a scalar

quantity?

A Speed

B Momentum

C Acceleration

D Force


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1.41.4Understanding measurementsUnderstanding measurements

Learning outcomes:

1. Measure physical quantities usingappropriate

instruments

2. Explainaccuracyand consistency

3. Explaintypes of experimental error

4. Use appropriate techniques to reduce errors


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MeasurementsMeasurements

y Physics is a science which involves

measurements of various physical

quantities

y Measure physical quantities using

appropriate instrument suchas:-

1. A measuringtape

2. A metre rule3. A vernier callipers

4. A micrometer screw gauge


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1. Measuringtape1. Measuringtape

y Measuringlongdistance suchas length

and width of classroom

y Has anaccuracy of 1 cm


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2.2. MetreMetre RuleRule

y Measure length from a few cm up to 1 m

y Has anaccuracy of 0.1 cm ( 1mm)

y Precaution:-1. Avoid parallax errors

2. Avoid end errors


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3.3. VernierVernier CallipersCallipers

y Measure an object withdimensions up to 12.00 cm

y Has anaccuracy of 0.01 cm

y To measure the internal or externaldiameter


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3.3. VernierVernier CallipersCallipers

y Main scale 5.3 cm

y Vernier scale 0.07 cm

y Vernier scale reading = main scale + vernier scale

= 5.3 cm + 0.07 cm= 5.37 cm


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4. Micrometer Screw Gauge4. Micrometer Screw Gauge

y Measure smalllength between 0.10 mm and 25.00 mm

y Measures the diameter andthickness

y Has anaccuracy of 0.01 mm


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4. Micrometer Screw Gauge4. Micrometer Screw Gaugey Main scale (sleeve) = 2.50 mmy Thimble scale = 0.09 mm

y MSG reading = main scale + thimble scale

= 2.50 mm + 0.09 mm

= 2.59 mm

mm

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