02 01 Fisika Dasar 1 - Besaran Dan Satuan

Welcome to the online lecture series of

Basic Physics 1.

In this video, we will discuss a

topic regarding quantities and units.

Physics is a basic science and is the

root of several fields of science such as

chemistry, astronomy, and even biology.

Physics is also the basis of

technology and industry.

Developments in both of these areas

are marked by developments

in physics itself.

In general, in physics, we

always try to understand

existing natural phenomena. To then

look for a pattern related to the

phenomenon.

Then, with the help of

mathematical language,

we can engineer this

into a technology that can be

applied to various fields.

For example, the

following phenomena such as waterfalls and rainbows,

lightning, and even swimming fish,

have inspired various

technological discoveries that we

enjoy today. Starting from automotive,

electronic devices,

health,

and others.

Therefore, understanding

basic physics is important for those of us who will

enter the industrial world.

One part of basic physics that is

important to understand is

quantities and units.

Well, let's discuss more

about these quantities and units.

Physics is an experimental science.

As discussed previously,

we want to understand a natural phenomenon

and then engineer it so that it can be

beneficial for human life.

Well, in

relation to this, in

physics, if we want to understand a

system, whether its nature, phenomena, or

anything else,

then we have to disturb the

system and then

observe how it responds.

Let's see here, let's say there is a

system.

I would like to know what

the characteristics of the system are.

What are its characteristics?

Suppose I want to know

what its size is,

what its

thermal properties are, etc. So the

way I do it is by giving a disturbance in the form of

measurement.

So,

from this disturbance, the system will

respond which is the

measurement result.

In relation to measurement results, there are

two important things we need to know,

namely

what we are measuring, namely the

quantity,

and

how much quantity we are measuring. This means that

the results can later be compared with

others. That is the unit.

Well, now

we return to defining

quantities and units.

So, in a measurement we

obtain a result,

the quantity is

to describe what we measure,

and the unit is to determine the quantity

of what we measure.

Now, there are a few important things

regarding

this measurement.

Often we don't realize how

many very precise measurements

make modern life

possible.

For example,

every component of a mobile phone,

from the chip, memory, microphone to the

camera, is

highly dependent on a series of

infrastructures consisting of

process device materials and

scientific principles that are measurable and carefully tested

.

All of this is

to ensure

that

the phone can make calls,

send texts or access the internet.

This unit and precision have become the

cornerstone of human civilization in the modern era.

Without clear standards or references,

it is certain that our civilization could be

destroyed in an instant.

That is the importance of

these quantities and units.

So it is

necessary to have a

standard unit that applies

forever

and for everyone.

So it applies globally.

Therefore

we need an agreement on the standards

we will use.

Here we use what is called the

metric system or international system.

There are seven main quantities or

basic quantities that we need to know.

Yes, namely length

in meters,

mass in kilograms,

time in seconds, electric

current in amperes, temperature

in Kelvin, light intensity

in candela

and amount of substance in moles.

Each of these quantities

has a

standard unit, such as what the

reference is.

Of course, this Sir has undergone a

process of change

in order to achieve the goal of being

valid forever for

everyone.

Well, now let's look at one

example of

how the definition of

units

has changed.

We take the case of units of

meters for the length quantity.

So,

where does the 1 meter that we know today, which is our benchmark for measuring anything, come from? How

can people say that 1 meter?

Well, there is a history to this.

Initially here we see that

1 meter was

originally

defined as

1 per 10 million

of the distance along the Earth's surface

between the

North Pole

and the equator passing through the

Paris meridian.

Of course,

with conditions like this,

it is certain that

there is imprecision, there is uncertainty

in the value. Why? Because the benchmark is too

big

.

Yes, it's time to recalculate or

people want to double check that they have to

make such a trip. So

a simpler prototype was made

to describe

1 meter.

Here is the prototype.

However,

we know that when we make an

item as a benchmark, the

item will definitely

experience changes,

both physically and chemically.

So,

we try to change the object

into an

object that is resistant to

these changes. Here,

it is changed

by

converting the material into platinum

iridium and storing it in

certain conditions.

So, the length of this rod shows

one meter.

However, in order to achieve the goal at

the beginning, do not let anything change,

accept it forever,

then try to define one meter

through

physical phenomena, namely here

after the discovery of the laser,

the definition of one meter is

1,650,763.73

times the

wavelength of the red-orange light spectrum

from a krypton atom

in a vacuum like this.

Then,

as time went by,

the definition changed again.

Now associated with the speed of

light.

Yes, here.

Then, in 2019, there was a

redefinition of all

units, for one meter it was linked

to

existing natural constants.

So, try to ensure that the value

does not depend on time

and does not depend on

where. Well, here is the

final definition related to the speed of

light as well.

So, in relation to the redefinition,

here we see that

these are the

seven

basic units in SI:

kilogram,

meter, second, ampere, kelvin, mole and

candela,

whose definitions are

ultimately linked to the

constants

that

exist in nature, whose values ​​are

fixed. For example

here there is um

kilogram associated with Planck's constant

um mass

associated

sorry, meter associated with the speed of

light

here there is

um second with frequency

ampere with charge

um kelvin with um

Boltzmann's constant and others

here there are.

You can read more details about

this redefinition of basic units.

Well, now

in reality

not all places, not all conditions

always use units

in the international system.

There are some places and conditions that

use other forms of units

that are considered more suitable.

For example, in the United States the

British Engineering System is more often used

.

Maybe we often hear that

when we read data or read news

from America, they

define, for example, length in

feet, mass in pounds,

temperature not in Kelvin, Celsius

but in Fahrenheit, like that, right?

Well, this is an

example.

Or in industry we often

find

quantities that are not in the

basic quantities in SI.

Often it is its

derivatives

that are used to

best describe the condition of a system.

For example,

if we play or we

see a machine, we often

read the

term horsepower.

This is just a conversion

that one horsepower is equal to

745.7

watts.

Why use horsepower?

This is to illustrate

how the

engine performs compared

to horsepower. We know that

before the steam engine existed by James Watt,

which was used as a

term for an engine for a vehicle or

anything using horse power.

When it was converted to a machine, then

people wanted to see how

its capabilities compared to the

previous, which was a

horse, something like that.

Another one is suppose this has

RPM.

We often hear

RPM

when talking about engine speed

and so on.

This is

rotation or revolution per minute,

revolutions per minute.

That is to describe

how many times a machine can rotate

in one minute.

Then another example is when

you build a factory or

are in an industrial area,

you must have heard of the

noise level.

Well, here we can see there is a table

here.

A table that we can easily

imagine the value of because it is

scaled

in tens like this.

So if it's 130,

40, it's easy to imagine

the comparison. Well, this is

in decibels, it's about the level of

sound intensity.

We often talk

about sound intensity. Well, it is

differentiated by level, yes. If

that's the level.

In decibels it is a

logarithmic scale of the ratio between the

intensity of

a place and

its threshold intensity.

So for intensity itself, the unit

is

watts per square meter.

So we can differentiate between

sound intensity and sound intensity level.

Don't let it happen that we often get

the terms mixed up. Another example is

we talk about mass

and weight.

In Indonesia, we make it the same. Suppose

how much do you weigh?

Oh, 50 kg. Well, that's

wrong.

Because weight is a

force. The unit is Newton.

If the kilogram is mass.

Yes, so often

physically we are wrong actually. So

by learning this,

you will definitely be able to improve how you

define the terms for

unit quantities.

Well, then

we here

often encounter

diverse values. So, the

measured quantities

in real life have a

very wide range.

From the very big to the

very small. Like

in the

real world, there are objects that are

very small, there are objects that are

very large. That's a huge

scale of scope.

Therefore

we need some

help to accommodate values

that are either too large or too small

to be easily written in

standard decimal notation.

Example.

We are talking about electrical power

in watts.

We can talk about this electrical power

on a large scale or a small scale.

For example,

we are talking about the electrical power

generated by a

geothermal power plant.

This is an example at the

Wayang Windu Geothermal Power Plant.

Or on a smaller scale, we are talking

about the electrical power of a

medical device implanted into the body.

An example of this is a pacemaker.

Of course the power value must be very

different.

For power plants, the

value is 227

million watts.

For

pacemakers, the value is

0.0001

watts.

So, to accommodate values ​​like

this which have too many zeros,

we can use something called

scientific notation.

Besides simplifying the writing method,

it also makes it easier for us to

imagine

the scale.

So it's time for us to see what the

order of magnitude is.

Yes, this is clear, right? This is 10^6,

this is 10^-4. Of course this is a

very large value and this is a very

small value.

Apart from that, in this concept we also

know something called a prefix. So

this value of 10 to the power has its

own name.

The term

is called a prefix. For example,

I can change these two values ​​to something

like this.

So 10^6 is called mega, so 27

MW.

I changed the one below to 100 *

10^-6.

-6 to micro.

Well,

we will learn about

scientific notation and prefixes.

Okay, now let's look at

scientific notation.

Well, in general,

scientific notation is written in the form

A multiplied by 10^B.

Where A is a real number.

So the value can be from

minus to positive.

Can be commas, can be whole numbers.

While B is an integer.

Of course it can be positive and negative.

For example, we can see here.

Suppose

10

thousand.

We convert it into

scientific notation form. Here we can

see it becomes

1 * 10 ^ 4. Where from?

We want to make this one in front,

okay? That means this one

moved here.

Meanwhile, we change the zero to 10 to the

power of 10. This means there are 1 2 3 4.

This means there are 10 ^ 4.

Another example.

75 million.

Suppose

I want the front number in

scientific notation

to be 75.

So this is 75. The

remainder is that we have 1

2 3 4 5 6 zeros. So this is 10 ^ 6.

Now, what if I don't want the front number to be

75, but I want it to be

7.5, for example this one.

So 7.5

means 75, but the comma is here, right?

So

what is the number after the comma here?

1 2 3 4 5 6 7. So this means 10 ^ 7.

Or maybe this was 10 ^ 6 initially, right?

If a comma moves back

here, then the exponent increases by one.

If there is a zero added to

the right, the exponent will reduce by one.

Another example.

0.001.

So the example here is that we want

to keep the number one in front here.

This means that there is

no comma behind the number one,

right? This means that the comma must

be moved until it disappears. How

to do?

We shift this comma 1

2

3 times. So this is 10 to the power of

minus 3.

Another example here, let's say

0.000009.

How do you get here?

So, for

example, if I want this to be 9,

that means there is no comma before 9, right

here, right.

This means the comma must be removed, we

move 1 2 3 4 5 6 times. That means

this is minus 6.

Yes.

Another example is this 0.00025,

meaning

if I want the front to be 25, there is no

comma behind it,

meaning we remove the comma 1 2 3 4 5.

What if I want it to be 0,

sorry, 2.5, like this. That means the comma is

between 2 and 5, right? This means we

shift the comma to between 2 and 5.

This means 1 2 3 4 times. If it means something

like this.

If it's 0.25, you should be able to

define it too. Like that, yeah.

So, now that you have a

form of scientific notation, how do you

operate it?

There are several properties.

If you multiply like this,

it means that if you multiply the

scientific notation form, then

multiply the front part as usual

A times C

, so the exponent becomes the sum.

For example, suppose

I have

eee suppose here there is

2

times 10 to the power of 3

I want to multiply it

by suppose this is 3 times 10 to the power of

minus 2 suppose that

means the result is

2 times 3 first 6

multiplied by 10 to the power of what? The power is

added

3 plus minus 2

then the result is 6

times 10 to the power of 3 plus minus 2 is

1

that is yes

next

division

we divide the front number first then the

power becomes a subtraction form

for example I have for example

eee 12 times 10 to the power of

6 divided by

4 times 10 to the power of minus 3 for example yes

means the result is the same as

12 divided by 4

times 10 to the power of 6 minus minus 3

the result is the same as

meaning

3 times 10 to the power of 6 minus minus 3

nine like that yes

finally

if the power yes for example here the power of

A times 10 to the power of B are all

raised to the power of K

then

raise the power first the power of the

front number then the

power is

multiplied for example for example

2 times 10 to the power of 5

squared is equal to meaning

2 squared multiplied by

10

^ 5

^ 2 yes multiply 2 is equal to

4 * 10 ^ 10

Well, that's how to write

the conversion into scientific notation and

operate it. We will

encounter many values ​​like this

in the following sections.

So,

after we got to know about

scientific notation, we also got to know

here what is called a prefix or prefix.

So, the multiplication factors 10^

have their own names, their

own prefixes.

Which is the prefix for the unit.

Suppose I have a quantity

that is measured, the result is, for example,

I get 10^-9

m

or, for example, eh, don't, for example, 2 *

10^-9

m.

So

10^-9 is nano. But I

mentioned earlier that the value is the same

as

2 nm.

So

this exponent value is changed to the

nano prefix or I measure I have a value

for example

emm

7 * 10^

9

watts of

electrical power, right.

So in what form should I write it

? 5 in front of it is

giga watt. like that.

Yes, so just change it.

Roughly, yes, later the values ​​that

you need to understand are quite a few parts, maybe

kilo, mega, giga, nano, micro, milli.

That's what we'll use often later.

Well,

in

physics we often encounter

many symbols. These symbols are used

to describe

both quantities, prefixes and

other things.

Well,

these symbols, apart from using the

alphabet

that we know

A, B, C, D, E to Z,

also use the Greek alphabet.

Well, here is an

example

of the

Greek alphabet.

Yes, starting from alpha,

beta,

gamma, delta,

to omega.

Surely you are already familiar

with some of the

letters here, right?

But there are also parts that are not. Well,

here the example

is given that the letter on the left

is the capital letter, the letter

on the right is the lower case letter. Maybe

we meet lowercase letters more often

.

Well, some examples that you are probably

familiar with include the first one,

lambda.

We often use the lowercase lambda

in the

wave concept to represent eh

as a symbol for wavelength.

Another example is

rho.

If rho is roughly what

we are talking about in terms of

density, density, right?

Another one that we may

encounter frequently is

omega.

Both capital and lower case letters

.

Where do

you find the capital omega?

This is the unit for

electrical resistance, right? For example, if

there is a 7 ohm resistor, that's omega, right?

Where are the lowercase letters? We can

meet this small letter omega in

the concept of waves as well

or the concept of rotational motion regarding

angular velocity or

angular frequency. That's how it is. So I

hope you are starting to get familiar with

this Greek alphabet. How to

write it and how to

read it. Also what symbol is he.

Okay, now that we know some

basic concepts

we will move on to the

physics part.

So,

as an introduction,

we will get to know

what is called idealization and modeling.

So

various physical systems can be

simplified into a model.

What for?

To avoid

overly complicated analysis.

For example, a simple thing

is actually complicated physically.

For example, you throw a ball.

If you throw a ball, let's say it

's a baseball.

So what happened there? First,

there are several physical phenomena,

namely, first the ball rotates.

Yes, it rotates about

its axis.

So the ball doesn't stay in

position.

Then

and he there are complex shapes. what

this means is that this ball may not be

100% a

perfect ball shape, there are dents on the

sides,

there are seams here, it's

quite a complex shape.

Then don't forget that there

must be a factor of air friction and

wind.

He exerts a force on the ball,

either as a drag

or

eh, making the ball

move in a complicated way.

Yes.

Then there is also the gravitational force that

works depending on the height.

Because

the higher the ball is from a reference point,

for example the ground surface, the

gravitational force will actually

decrease.

So here it is seen that there are many

phenomena that need to be taken into account.

But

in this fundamental physics in particular

we utilize idealization and

modeling. So we assume the conditions are

ideal

so that

we can model the system in a

simple way. Like what?

Like this.

Okay.

We assume or idealize. What is the

ideal?

Assumption. Yes, firstly, the ball that

has a

complex shape, there are dents, there are

seams, we consider it as a

point or particle object.

So if the object is a point or particle,

we don't need to or we won't be

able to see its rotational motion.

This means that

the direction of the ball's movement is only

this green arrow.

There is no direction in which the ball rotates.

One.

So, we can eliminate the

rotational motion factor.

The second is

idealization, we ignore air friction.

So what?

One of the forces at work is missing.

There is no air friction force.

Here, okay?

Third, we assume that the

gravitational force acting on the ball is

constant. So, even though the ball changes

height, the

gravitational force remains the same value.

So that in the end this system

becomes very simple and we can

analyze it much more easily.

Of course,

as you study physics more

advancedly,

these factors will start to come

into play. So that when we

encounter a real case

,

we can get results that are

close to reality.

But of course,

this simplification

usually doesn't change the

real value very much. That's how it is

.

Besides talking about

idealization and modeling, we also need to

talk more about a reference point.

So, later in defining

several quantities in physics,

we must have a common reference point

. So that

later we can easily

analyze, to identify

physical quantities, especially later

in motion.

The frame of reference we use is

a Cartesian coordinate system

, yes. There are actually many

coordinate systems, yes.

There are Cartesian, there are polar, there are cylindrical,

and there are spherical. Let's just use the

simplest one.

For example, let's say I have

coordinates in two dimensions, namely

Cartesian, there are two x-axis and y-axis

which are perpendicular to each other.

Suppose there is a ball at point A.

In two-dimensional Cartesian coordinates,

I can define this object to be

at positions

xA

and yA, so the points are xA,yA.

For three dimensions,

we add one more axis,

besides x,

y, there is also z.

Suppose there is a ball at point B, then

I can determine its position on each

axis,

at xB with respect to the x-axis, with respect to the

z-axis at zB, with respect to the y-axis

at yB. This means the position is

xB,yB,zB.

Well,

later this framework or coordinate system

is what we will use

while

studying

some parts of basic physics.

OK,

so far you have learned

a little about quantities and units.

You can look for various

other explanations in various sources,

both books

and

other videos.

Okay, that's it for

this video.

Happy learning and see you in the

next video.

Thank You.