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1.2 Base & Derived Quantities1.2 Base & Derived Quantities
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Chapter 1 Chapter 1 Introduction To PhysicsIntroduction To Physics
Learning OutcomesLearning Outcomes
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PHYSICAL QUANTITYPHYSICAL QUANTITY
Wow! Is this real??!
Hehehe…. Can u guess what is my
height?
Weight Mass Timewww.myfunphysicsworld.blogspot.comwww.myfunphysicsworld.blogspot.com
PHYSICAL QUANTITYPHYSICAL QUANTITY
The quantity that The quantity that can be measuredcan be measuredMeasurable :Measurable :The process of determining the The process of determining the value of a quantity using a scientific value of a quantity using a scientific instrument with a standard scaleinstrument with a standard scaleExample:Example:Mass, weight, height, time, Mass, weight, height, time, temperaturetemperature
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Length of meter ruler = 100.0 cmLength of meter ruler = 100.0 cm
Which isWhich is
1. Physical quantity?1. Physical quantity?
2. Numerical value?2. Numerical value?
3. Unit of measurement?3. Unit of measurement?
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Non-physical QuantityNon-physical Quantity
The quantity that The quantity that cannot be cannot be measuredmeasured..
Example:Example:
Feelings-happy Feelings-happy , sad , sad , , angry ….angry ….
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Physical Quantities
Base Quantities Derived Quantities
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Base QuantityBase Quantity Derived QuantityDerived Quantity
Physical quantities Physical quantities that that cannot be cannot be defineddefined in terms of in terms of other other physical physical quantitiesquantities
Physical quantities Physical quantities derived from base derived from base quantitiesquantities by by multiplication or multiplication or division or bothdivision or both
Length, Mass, Length, Mass, Time, Time, Temperature, Temperature, Electric CurrentElectric Current
Density, Pressure, Density, Pressure, Force….Force….
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Base QuantitiesBase QuantitiesPhysical quantities that cannot be defined Physical quantities that cannot be defined in terms of other physical quantities.in terms of other physical quantities.Unit : base unitUnit : base unit
Name & SymbolName & Symbol S.I. Unit & SymbolS.I. Unit & Symbol
Length / lLength / l meter / m meter / m
Mass / mMass / m kilogram / kgkilogram / kg
Time / tTime / t second / ssecond / s
Temperature / TTemperature / T kelvin / Kkelvin / K
Electric Current / Electric Current / II ampere / Aampere / Awww.myfunphysicsworld.blogspot.comwww.myfunphysicsworld.blogspot.com
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Derived QuantitiesDerived QuantitiesPhysical quantities derived from base quantity Physical quantities derived from base quantity (multiplication or division or both)(multiplication or division or both)
Unit : Derived UnitUnit : Derived Unit
Name & SymbolName & Symbol S.I. Unit & SymbolS.I. Unit & Symbol
Velocity / vVelocity / v meter per second / msmeter per second / ms-1-1
Force / FForce / F Newton / NNewton / N
Pressure / PPressure / P Pascal / PaPascal / Pa
Weight / WWeight / W Newton / NNewton / N
Density / Density / ρρ kg mkg m-3 -3 www.myfunphysicsworld.blogspot.comwww.myfunphysicsworld.blogspot.com
DERIVED QUANTITIESDERIVED QUANTITIES
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(a) Show the relationship between the (a) Show the relationship between the following derived quantities and their following derived quantities and their corresponding base quantities.corresponding base quantities.
(b) Derive the units for the following (b) Derive the units for the following physical quantitiesphysical quantities
Density Density = mass / volume= mass / volume
= mass / (length)= mass / (length)33
= kg m= kg m-3-3
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PrefixPrefix SymbolSymbol ValueValue
TeraTera TT 10101212
GigaGiga GG 101099
MegaMega MM 101066
KiloKilo k k 101033
HectoHecto h h 101022
DecaDeca dada 101011
DeciDeci d d 1010-1-1
CentiCenti cmcm 1010-2-2
MilliMilli mm 1010-3-3
MicroMicro ųų 1010-6-6
NanoNano nn 1010-9-9
picopico pp 1010-12-12
4amanah 10jan until here4amanah 10jan until here
Ask them to memorise prefixes follow text Ask them to memorise prefixes follow text bookbook
Ask to collect rm1 by next weekAsk to collect rm1 by next week
30 students30 students
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Changing UnitChanging Unit
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PrefixPrefix ValueValue
Tera / TTera / T 10101212
Giga / GGiga / G 101099
Mega / MMega / M 101066
Kilo / kKilo / k 101033
Hecto / hHecto / h 101022
Deca /daDeca /da 101011
Deci / dDeci / d 1010-1-1
Centi/cmCenti/cm 1010-2-2
Milli / mMilli / m 1010-3-3
Micro / Micro / ųų 1010-6-6
Nano / nNano / n 1010-9-9
Pico / pPico / p 1010-12-12
10-6-(3) =10-9
1.23 ųmųm
= 1.23 x 10-6-(3) km
= 1.23 x 10-9 km
10(A) -(B)
A = initial prefix
B = final prefix
1.23 ųm ųm = _____ km
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PrefixPrefix ValueValue
Tera / TTera / T 10101212
Giga / GGiga / G 101099
Mega / MMega / M 101066
Kilo / kKilo / k 101033
Hecto / hHecto / h 101022
Deca /daDeca /da 101011
Deci / dDeci / d 1010-1-1
Centi/cmCenti/cm 1010-2-2
Milli / mMilli / m 1010-3-3
Micro / Micro / ųų 1010-6-6
Nano / nNano / n 1010-9-9
Pico / pPico / p 1010-12-12
106-(-9)= 1015
4.56 Mg
= 4.56 x 106-(-9)
= 4.56 x 1015 ng
4.56 Mg = _____ ng
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Change to S.I. UnitChange to S.I. Unit
456 g/cm456 g/cm33
= = 456 g456 g
cmcm33
= = 456 x 10456 x 10-3 -3 kgkg
1 x (101 x (10-2-2 m) m)33
= = 456 x 10456 x 10-3 -3 kgkg
1 x 101 x 10-6-6 m m33
=456 x 10=456 x 10-3 -3 x 10x 1066 kg m kg m-3 -3
= 456 x 10= 456 x 1033 kg m kg m-3 -3
= 4.56 x 10= 4.56 x 1055 kg m kg m-3-3
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Exercise 1Exercise 1
January 2011January 2011
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For the following physical quantities, For the following physical quantities, derive theirderive theiri) base quantitiesi) base quantitiesii) units ii) units
(a)(a) VelocityVelocity
(b)(b) AccelerationAcceleration
(c)(c) ForceForce
(d)(d) WorkWork
(e)(e) DensityDensity
1
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Derived Quantities
Base Quantities Units
a)Velocity displacement/time= length/time
m/s
b) Acceleration
c) Force
d) Work
e) Densitywww.myfunphysicsworld.blogspot.comwww.myfunphysicsworld.blogspot.com
(a) Velocity(a) Velocity
= displacement/time= displacement/time
= length/time= length/time
= m/s= m/s
= m s= m s-1-1
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(b) Acceleration(b) Acceleration
= = Change in VelocityChange in Velocity
timetime
= = lengthlength
(time)(time)22
==m/sm/s22
==m sm s-2-2
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(c) Force(c) Force= mass x acceleration= mass x acceleration
= mass x = mass x lengthlength
(time)(time)22
= kg m s= kg m s-2-2
= Newton= Newton
= N = N
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(d) Work(d) Work
= Force x Displacement= Force x Displacement
= mass x acceleration x length= mass x acceleration x length
= mass x = mass x lengthlength x length x length
(time)(time)22
== kg m kg m22 s s-2-2
= Nm = J= Nm = J
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e) Densitye) Density
= = massmass
volumevolume
= = massmass
(length)(length)33
= kg m= kg m-3-3
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Derived Quantities
Base Quantities Units
a)Velocity displacement/time= length/time
m/s
b) Acceleration Change in Velocity/time= length/(time)2
m/s-2
c) Force Mass x acceleration= (mass)(length) (time)2
d) Work Force x displacement=
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Show the relationship between Show the relationship between the following derived the following derived quantities and their quantities and their corresponding base corresponding base quantities.quantities.
(a) acceleration(a) acceleration(b) momentum(b) momentum
2
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