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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