STEEMIT PHYSICS CLASS | LESSON 2 - CLASSIFICATION OF QUANTITIES AND UNITS.

Hello Everyone, you are welcome to Steemit Physics Class with @whileponderin. In the last class, we began by introducing the Subject Physics, what it entails and the activities in our daily lives where it is applied. We also mentioned the branches of Physics, and we discussed in detail what Quantity and Units stands for. Finally we concluded by defining what an S.I unit.

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Just as promised, in today's class, we will discuss more on these quantities and Units, as well as their classifications. If you haven't read the last class, you can read about it here Lesson 1: Introducing Physics

CLASSIFICATION OF QUANTITIES AND UNITS

Quantities in Physics are classified in two ways. Those classifications are:

1. Based on their dependency on other quantities.

2. Based on their direction.

We will now talk about these two classification in detail.

Based On Their Dependency On Other Quantities

Based on how dependent quantities are to another, we have two types of quantities. They are:

a. Fundamental Quantities and Units:-

These quantities are those quantities that are independent of other quantities. This means that they are not defined in terms of other quantities neither are they derived from other quantities. It is from them that other quantities are derived from. The S.I units of these type of quantities are known as fundamental units.

b. Derived Quantities:-

These quantities are those quantities that are dependent of other quantities. This means that they are defined in terms of other quantities, and also they are derived from other quantities. They are mostly obtained by combining fundamental quantities or a fundamental quantity and a derived quantity.The S.I units of these type of quantities are known as derived units.

Starting from where we stopped last week, we made mention that classifying every thing into quantities and units makes every concept in physics very easy to measure. In the last class we talked about the issues that scientists faced for having different S.I unit and they came together in france (1960) to decide the S.I unit of 7 quantities.

Those measuring quantities and the units they were assigned are:

Fundamental Quantity	S.I Units	Unit Abbreviation
Length	Meter	m
Mass	Kilogram	s
Time	Second	Kg
Electric Current	Ampere	A
Temperature	Kelvin	K
Luminous Intensity	Candela	cd
Amount of Substance	Mole	mol

These 7 quantities they decided on are called fundamental or basic quantities. While their units are referred to as derived units.

Derived Quantities on the other hand are made by combining two fundamental quantity or a fundamental and a derived quantity. Below is a table illustrating this.

Derived Quantity	Derivation	Derived Units
Area	Length × Breadth	m^2
Volume	Length × Breadth × height	m^3
Velocity	Displacement/time	m/s
Speed	Distance/time	m/s
Density	Mass/Volume	kgm^-3
Acceleration	velocity/time	m/s^2
Force	mass × acceleration	Newton (N)
Energy/Work	Force × distance	Joule (J)
Power	Work/time	J/s
momentum	mass × velocity	kgm/s
Pressure	Force × Area	Pascal (Pa), N/m-2
Frequency	no of oscillation/time	s^-1
Electric Charge		Coulomb (C)
Voltage		Volt (V)

From the table above, you can see that the derived quantities are obtained by combining two fundamental quantities or a fundamental quantity and a derived quantity.

Based On Their Direction

Physical quantities can also be classified based on if they have direction or not. They are:n

a. Scalar Quantities:

Scalar Quantities are those quantity that have magnitude (numerical value) but have no direction. This means

Examples of scalar quantities includes:

i. Energy
ii. Length
iii. Density
iv. Mass
v. Speed
vi. Temperature
vii. Time.
viii. Volume.

Considering the examples above, you will notice that you can tell their numerical value or magnitude, but you can't tell their direction. For instance, you can tell the numerical value of time but you can't tell the direction of time, whether it's to the east, west, north or south.

b. Vector Quantities:

Vector Quantities are those quantity that have both magnitude (numerical value) and direction. This means

Examples of Vector quantities includes:

i. Displacement
ii. Acceleration
iii. Velocity
iv. Force
v. Weight
vi. Momentum
vii. Electric Field.

Take for instance Displacement and Distance. Both of them talks about moving from one point to another. The only difference is that displacement in addition to the numerical value of the length covered, it also talks about the direction moved (whether east, west, north and south). But distance doesn't talk about direction moved.

IN SUMMARY

In today's class, we began by revising what we learnt in the previous class. From there, we began to discuss the different classifications of physical quantities; based on direction and based on how the units are derived.

In our next class, we will discuss more on how these quantities are measured as well as how Units, as well as how to derived their dimensional Analysis.

To check your progress for this lesson, try out these activities.

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ACTIVITY

1. What's the difference between fundamental and derived quantities?

2. List three examples of fundamental quantities and their units?

3. List three examples of derived quantities and their units?

4. What's the difference between Scalar and Vector quantities?

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INTERESTING SCIENCE FACT: Did You know that...

Every year you will eat about 500 kilograms (1,100 pounds) of
food.That’s about the same weight as a small car!

_Source

I hope you found this class informative. See you next time

Read, Ponder, Love. © whileponderin