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Name : K.Veera NarayanaDesignation : Lecturer in PhysicsInstitute : GPW,Bheemunipatnam.Branch : Chemical Engineering.Year : I yearSubject : PhysicsSubject Code : CH-103Topic : Units and DimensionsDuration : 50 MtsSub-topic : Physical QuantitiesTeaching aids : PPT, Animation, Photographs.

Department Of Technical EducationAndhra Pradesh

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OBJECTIVES

On completion of this period,you would be able to understand

• Definition of a physical quantity

• Fundamental quantity

• Derived quantity

• System of units

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INTRODUCTION

A higher level of Technology is achieved by

• Using Precision measurement techniques• Accurate measurement of physical Quantities• Sustained development of basic sciences &

engineering.

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• What is a Physical Quantity?

• Examples of Physical Quantities

• The necessity of measuring Physical Quantities

Let Us Know

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Physical Quantity

• Any quantity which can be measured directly or indirectly is a physical Quantity.

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Some Physical Quantities

• Mass

• Length

• Time

• Temperature

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• Speed

• Acceleration

• Force

• Work

• Pressure

• Electric current

Some Physical quantities

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Necessity of measurement

Measurement of a physical Quantity enables us to

• Know the size of the quantity

• Understand the quantity comprehensively

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Unit of a Physical Quantity

Unit is a standard quantity used to• Compare and measure a physical Quantity.

For example:

• Kilogram is the standard unit to measure Mass.

• Meter is the standard unit to measure length

• Second is the standard unit to measure Time.

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Characteristics of a unit

A unit must be• well defined

• easily reproducible

• internationally Acceptable

• invariable.

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Classification of physical Quantities

Physical Quantities are of two types.• Fundamental Quantities.

• Derived Quantities.

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Fundamental Quantities

• Those Physical quantities which cannot be expressed in terms of any other physical quantities.

• Independent physical Quantities are called Fundamental Quantities.

Example :

– Mass

– Length

– Time

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Fundamental units

The units in which Fundamental Quantities are measured

• For example :

• Kilogram for Mass

• Meter for Length

• Second for Time

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Derived Quantities

• Physical Quantities depending on one or more Fundamental Quantities.

• Obtained from Fundamental Quantities.

Example :

• volume

• speed

• force

• pressure

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Derived Units

The Units of Derived Quantities.• For example,

------ For volume

m/s ------ For speed

Newton ------ For force

N/m2 ------ For pressure

3m

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Systems of Units

There are 3 old systems of units.

• C.G.S. system ----- Centimeter Gram Second system.

• F.P.S. system ----- Foot Pound Second system• M.K.S. system ----- Meter Kilogram Second system.

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S.I Units( International System of Units )

• S.I.Unit system was adopted in, 1960

• They are ‘International System of Units.’

• Applicable to all branches of Science & Engineering.

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Summary

We have learnt about• Physical Quantities

• Unit of physical quantity

• Fundamental and Derived Quantities

• Systems of Units

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Frequently asked questions

• Define Physical Quantity. Give examples.

• Define unit of a Physical Quantity.

• Define Fundamental Quantities. Give examples.

• Define Derived Quantities. Mention two examples.

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Quiz

1. Which of the following is not a physical Quantity.

a) Mass b) Forcec) Mind d) velocity

Ans: c

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2. Which of the following is a Fundamental Quantity.

a) Force

b) Length

c) Speed

d) Volume

Ans: b

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3. Which of the following is a Derived Quantity

a) Mass

b) Time

c) Pressure

d) None

Ans:c

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4. Identify the Fundamental Unit from belowa) Kilogrammeb) Meterc) Bothd) None

Ans: c

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5. Identify the derived unit from the following

a) Newton

b) Kg/m3

c) Meter3

d) All

Ans: d

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THANK YOU