PHYSICAL QUANTITIES AND MEASUREMENT.pptx

MADE BY MANAHIL OSAMA(Grade
8th)

 “physics is defined as study of matter, energy and their mutual
interactions”
 Physics is derived from Greek word physikos meaning the science of
natural things
 Physics is also considered as the study of the properties of matter,
space and time.
 In physics we study a wide range of phenomenon associated with
objects as small as sub-atomic particles and as large as galaxies.
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 Physics is divided into further branches to facilitate its study.
 CLASSICAL PHYSICS:
 Classical physics deals with the principles developed in many
branches of physics before 20th century.
 Branches of classical physics:
 There are 7 branches of classical physics.
1. Mechanics
2. Heat
3. Thermodynamics
4. Sound
5. Optics
6. Electromagnetism
7. Atomic physics
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 MODERN PHYSICS:
 The development made in 20th century are studied
under the heading of modern physics.
 Branches of modern physics:
 There are 6 branches of modern physics.
1. Nuclear physics
2. Solid state physics
3. Semi-conductor physics
4. Low temperature physics
5. Particle physics
6. Plasma physics

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 Interaction of physics with other sciences such as
Astronomy, Biology, Geology and Chemistry etc have
evolved interdisciplinary fields.
 This list of such subjects is growing continuously.
 Interdisciplinary fields:
 There are 5 interdisciplinary fields.
1. Astrophysics
2. Bio-physics
3. Chemical physics
4. Geo-physics
5. Medical physics

 Physical quantities are those quantities which can be
measured or the property of matter. E.g. length, mass,
time ,volume, density, velocity, temperature,
acceleration etc.
 A physical quantity is represented by a number
followed by a proper unit
 This number represents the size or magnitude of
physical quantity with a proper unit.
 The number alone is meaningless.
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 Types of physical quantities:
Physical quantities are classified into two groups:
1. Base Quantities
2. Derived Quantities
 Base quantities:
 Those physical quantities in terms of which other
physical quantities can be measured are called base
quantities.
 There are seven quantities such as length, mass,
time, electric current, temperature, amount of
substance, intensity of light.
 Derived quantities:
 Those quantities which can be derived from base
quantities are known as derived quantities.

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 Length, mass, volume, work, power, pressure, force
etc. are examples of derived quantities.
 Derived quantities can be obtained by combination of (
multiplication or division) two or more than two base
quantities.

 The international system of units with the
internationally accepted abbreviation SI is the modern
version of the metric system.
 This was recommended by the 11th general conference
of weights and measures held in Paris in 1960.
 This is widely used system of measurements in science
and technology through out the world.
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 Base units:
 The unit of base quantity is known as base unit.
 There are 7 base units.
QUANTITY UNIT
Name of base quantity Symbol Name of unit Symbol
Length l metre M
Mass m Kilogram kg
Time t second S
Electric Current I ampere A
Temperature T kelvin K
Amount of Substances n mole mol
Intensity of Light L candela cd

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 Derived units:
 The units of a derived quantity are as derived units.
 There are several derived units.
QUANTITY UNIT
Name symbol Name Symbol
Area A Square meter m^2
Speed V Meter per second ms^1
Acceleration a Meter per second square ms^2
Force or weight F Newton N/kg m s^2
Pressure p Pascal Pa or N m^2
Work or energy W Joule J /N m
Power P Joule per second J s^1
Charge Q Ampere second /coulmb A s /C

 The prefixes are very useful in expressing a
physical quantity which is either very small or
very large.
 Prefixes are the words or letters such as mega,
kilo, centi, milli and micro etc added before S.I.
units of a physical quantity.
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 Scientific notation is commonly referred to as
“Standard Form”.
 In scientific notation we express the given number as
some power of ten multiplied by a number lies
between 1 and 10.
 For example: The radius or earth is about 6370000m.
 The given value in scientific notation can be written as
6.37*10^8.
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 A measuring instrument is a device used to measure a
physical quantity.
 Measuring tape, metre rule, vernier calliper, screw
guage and travelling microscope etc are used for
measurement of length.
 Measuring cylinder, burette and pipette are used for
measurement of volume of liquid.
 Physical balance, beam balance and digital balance are
used to measure the unknown mass.
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 Clock, watch, stop watch and digital watch etc are used
to measure the duration of an event.
 Measurement of length:
 Metre rule:
 The metre rule is used to measure the length of an
object or distance between two points.
 It consists of 1m (100cm).
 Each centimetre is divided into 10 equal parts called
millimetre. 1mm is the least count of the metre rule.

USE TO MEASURE THE LENGTH OF OBJECT OR DISTANCE
BETWEEN TWO POINTS.
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 Measuring tape:
 A measuring is flexible ruler and consists of thin and
long strip made of cloth, plastic or steel with calibrated
scale on it.
 The least count of the measuring tape is 1mm.
 It is available in wide range of lengths such as 10m,
20m, 50m or 100m.

USE TO MEASURE THE LENGTH WITH THE LEAST COUNT OF
Imm.
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 Vernier calliper:
 Vernier callipers is a device which can be used for precise
measurement of length.
 It can measure accurately up to (1/10th ) of a mm (0.1mm) .
 The use of vernier callipers is to measure the internal and
external diameter and depth of an object.
 Parts of vernier calliper:
 It consists of 6 parts.
1. Main scale
2. Vernier scale
3. Fine adjustment screw
4. Locking screw
5. Jaws
6. Strip or depth guage

USED TO MEASURE LENGTH WITH THE LEAST COUNT OF
0.1mm
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 Micrometer / screw guage:
 A screw guage also known as micro meter is another precise
length measuring instrument .
 It is used for measuring small widths with an accuracy of
0.01mm / 0.001cm.
 Parts of screw guage:
1. Anvil
2. Spindle
3. U shaped frame
4. Lock
5. Main scale
6. Circular scale
7. Thimble
8. Ratchet

USE TO MEASURE LENGTH WITH THE ACCURACY OF 0.01mm
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 Measurement of volume:
 The space occupied by an object is defined as its
volume.
 The volume of an object does not depend on its mass.
 Two objects of same mass can have different volumes.
 Volume is a derived quantity and its SI unit is m^3.
 The smaller units of volume are cubic centimeter
(cm^3) and cubic decimeter (dm^3).
 The volume of a liquid enclosed in a container is equal
to the internal volume of the container.

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 One cubic decimeter (dm^3) has been assigned the name of
litre (L).
 One millilitre (mL) is equal to one cubic centimeter (cm^3).
 In laboratory the instruments used for measurement of
volume of liquid are measuring beaker, measuring cylinder,
measuring flask, burette and pipette.
 Measuring cylinder:
 A measuring cylinder is made up of transparent plastic or
glass which has a calibrated vertical scale.
 When a liquid is poured into measuring cylinder then
volume of liquid can be read directly on the marked scale.

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 The cylinders are available in variety of sizes ranging
from 100 mL to 2500 mL.
 Measuring cylinders provides a more accurate reading
of volume of liquid as compared with measuring
beaker or measuring flask.
 Measuring cylinder can also be used to measure the
volume of an irregular shaped solid indirectly by
measuring the displacement of a liquid produced by
the solid.

USED TO MEASURE THE VOLUME OF A LIQUID
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 Measurement of mass:
 The quantity of matter in an object is defined as its mass.
 Mass of an object can be determined by comparing it with a standard mass.
 Physical balance:
 The physical balance is based on the principle of moments i.e. the clock-wise
moments are equal to anti-clockwise moments for a beam which is in
equilibrium at a point.
 Parts of a physical balance:
1. Brass beam
2. Metallic pilar
3. Wooden base
4. Two pans
5. metallic pointer
6. Scale
7. Stirrup
8. Balancing screw
9. Plumb line
10. Knob
11. Leveling screw

USED TO MEASURE MASS
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 Measurement of time:
 Stopwatch:
 It is a special type of watch used to measure the duration of an event.
 This is named as stopwatch because it can be started or stopped
whenever required.
 There are two types of stopwatches i.e. mechanical or analogue and
digital.
 The least count of an analogue stopwatch is 0.2s.
 Before using the analogue stopwatch for measurement of duration of
an event ensure that both needles are at zero position.
 If you want to stop the stopwatch then press the knob.
 The working of a digital stopwatch is similar to conventional
stopwatch.
 A digital stopwatch can measure time with an accuracy of 0.01 second

USED TO MEASURE THE DURATION OF AN EVENT
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 In any measurement, the accurately known digits and
the first uncertain or doubtful digit in an expression are
called significant figures.
 For example: The diameter of metallic wire as
measured by a micrometer screw gauge is 2.65mm,
then there are three significant figures and the last digit
5 is uncertain or doubtful.
 The precision of a measured value of a physical
quantity is given by significant figures.
8th)

PHYSICAL QUANTITIES AND MEASUREMENT.pptx

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