MAGNITUDE AND UNIT

Standard Competency

1.1 Magnitude gauge and apply the unit

Basic Competency

1.1 Master the unit and magnitude

1.2 Use correct measuring device for measuring

CHAPTER I

MAGNITUDE AND UNIT

A.   MAGNITUDE AND UNIT

Physics requires thorough gaugings so that explainable studied phenomenon by accurate. Gauging is  the compare something with something else which  is considered as Lawson criterion.

Magnitude is something is measurable thing and expressed by number

Example: earth, long, thick, volume, and others.

Unit is a Lawson criterion for expressing a magnitude

1.  Fundamental Magnitude

Two types of magnitude in physics, they are fundamental magnitude and derivative magnitude. Derivative magnitude is the unit magnitude’s  unit has been defined before.

There are seven fundamental magnitude in unit system of SI is :

NO       FUNDAMENTAL MAGNITUDE       UNIT              SYMBOL OF UNIT

1         Length                                                     Meter               ( m)

2          Mass                                                       Kilogram          (Kg)

3          Time                                                       Sekon              (Second)

4          Strength of current                             Ampere              ( A)

5          Intensity Of Light                               Candela            (Cd)

6          temperature                                         Kelvin              (K)

7          Amount Of Matters                             Mole                (mole )

Besides the seven fundamental magnitude above, there are still is 2 additional magnitudes as complement, they are :

1.flat angle, the unit is radian ( rad)

2.angle solid , the unit is steradian ( strontium)

2.  Derivative Magnitude

Derivative magnitude is magnitude which the unit specified based on basic quantity unit. Some examples of derivative magnitudes we which have recognized, for example:

  • Speed of the unit m/s
  • Volume of the unit m3
  • The unit force of kg m/s2 or Newton ( Nitrogen)

In SI, there are some derivative magnitude which called the made moderate unit. For example standard unit of force is kg.m/s2 , hence moderation of the unit is newton ( N) or the unit of magnitude is kg.m-1.s-2 is simplification to become pascal ( Pa) . Generally this moderation taken away from the names of the scientiests, and as appreciation of their services as well.

B.  DIMENSION

Dimension is an magnitude expresses the  way of magnitude compiled by basic quantity.

Dimension can be searched from formula, unit and then dimension.

Dimension symbol of fundamental magnitudes.

NO   FUNDAMENTAL MAGNITUDE       UNIT AND THE SYMBOL    DIMENSION

1      Length                            Meter               ( m)                  [ L ]

2      Mass                               kilogram          ( Kg)                [ M ]

3      Time                               Sekon              ( second)         [ T ]

4      Strength of current     Ampere            ( A)                  [ I ]

5      Intensity Of Light        Candela           ( Cd)                [ J ]

6      temperature                  Kelvin              ( K)                  [ q ]

7      Amount Of Matters     Mole                ( mole)             [ N ]

Example of  Derivative Magnitude Dimension

1.Speed winze magnitude dimension = m/s = [ MT-1 ]

2.Volume= m3 = [ L3 ]

3. Force = kg.m/s2 = [ MLT-2 ]

Function Of Dimension

Intrinsically, function of dimension as examine :

1. To verify if the equation is correct or false

For example, equation of vanadium = vo + ½ a t 2, with v = velocity, a = acceleration, t = time.

Left joint dimension::                            Right joint dimension :

[  LT-1]                                                    [ LT-1] + [LT-2][T2]

[LT-1]            + [ L ]

from the result of examination, simply that  left joint dimension is not the same as. It means equation of continuity of wrong overhead. Correct of the equation of continuity is

v = vo + a t .

Left joint dimension::                            Right joint dimension:

[  LT-1]                                                     [LT-1] + [LT-2][T]

[LT-1] + [LT-1]

2. To check equivalence of two magnitudes which we doubt the truth

For Example, We doubt that equation of effort ( W = F.s) equivalent with equation of Potential Energy ( Ep = m. g. h).

Effort dimension::                                              Potential energy dimension:

[ MLT-2] [ L]= [= ML2T-2]                                   [M] [ LT-2] [ L]= [ ML2 T-2 ]

From the result of examination, simply that dimension of effort and potential energy dimension the same.

C. Unit conversion and unit system

Unit system which is often applied in some states differentiated by overhead of 3 system they are :

1.  Imperial System ( BGS : British Gravitational System)

2.  Metric System ( Metric System)

3.  International System

The difference between Imperial systems and Metric systems is which applied to comprehend, pay attention look at the  tables below/including  mechanics magnitude:

No   magnitude       Imperial Unit system     Metric    System

CGS               MKS

1      Mass                  slugging                            gram             Kilogram

2      Time                  Second                              Sekon           Sekon

3      Length               Foot                                 Centimeter     Meter

International System ( The) in fact retouching of unit system. Unit of si newly opened Internationally at Conference  General des Poids et Mesure in 1960 in sevres Paris

Imperial System  is used in English, American, and the ex- colonial countries. Hitherto this imperial system still up to now, especially in the fields of technics, Industrial, and Commerce.

To change the  imperial system become units which we apply ( MKS, CGS, or SI) required way so-called Converting Unit. Convert unit means to alter a unit to other unit by multiplying or dividing (Look at the unit conversion factors below, it can be used to change imperial unit into MKS unit, CGS and SI, or on the contrary. In this case, it will be limited on the unit conversion of  mechanics magnitude ( length, mass, time).

Length Unit conversion :

1 mile    = 1760 yards   = 1,609 km

1 yards   = 3 feet ( leg   = 0,9144 m

1 feet     = 12 inch        = 0,3048 m

1 inch    = 2,54 cm       = 0,0254 m

Mass unit conversion :

1ton       = 1000 kg

1 kuintal            = 100 kg

1pound  = 0,4536 kg

1slug      = 14,59 kg

Time unit conversion :

1 year    = 365 day

1hari      = 24 hour(clock

1 hour(clock      = 60 minute    = 3600 second

Example :

1. 36 Km/ hour(clock    = 36000 m / 3600 sekon = 10 m/s

2. 2 kuintal = 200 kg

D.  GAUGING

Accuracy of gauging device

Accuracy gauging result have become science demand. But that way, can be said that [there] no really accurate gauging, surely there is an uncertainty in the gauging result. Uncertainty in gauging result because accuracy ridge each device and also performance of us in reading result posed at by sizing device which we using.

Sizing device which we using determine gauging result which we get. Smaller accuracy scale at device which we used hence smaller the uncertainty number.

Length measuring device,

1.  Ruler

In general ruler uses scale  of cm up to mm. The accuracy limination of  gauging on ruler is 1 mm or 0,1 cm

2.  Slide calipers

Slide Calipers is length sizing device which is used applied for measuring external diameter of tube and the depth of hole. Ridge of accuracy of slide calipers of 0,1 mm or 0,01 cm. Slide calipers have 2 jaws they are is permanent jaw ( Principal scale) and shear jaw ( Scale nonius).

Look at picture above.

Reading result with slide calipers  is Principal scale + scale Nonius

X = 4,7+ (+ 4 x 0,01)cm

X = 4,7 + 0,04

X = 4,74 cm = 47,4 mm

Slide Calipers can be found in laboratories, now there are lot of slide calipers around us with level of higher accuracy , until 0,05 mm until 0,01 mm, or is also digital slide calipers.

3.  Screw Micrometer

Screw Micrometer has 2 scales they are principal scale and rotary scale. TheAccuracy limitation to 0,01 mm or 0,001 cm.

Look at picture above.

Reading result with screw micrometer to is Principal scale + scale Nonius

Y = 2,5 mm+ (+ 7 x 0,01)mm

Y = 2,5 + 0,07 mm

Y = 2,57 mm

Mass measuring device

For measuring mass substance can be applied various scales. There are some scale available for selected, for example spiral spring balance arm scale, etcetera.

Time measuring device

Stop watch or watch is time grader. Measuring device of watch up to 1 second, while stop watch has the accuracy of 0,1 second.

E.  IMPORTANT NUMBER

Important number is number which obtained from gauging result, including they lest questionable is number

The many important is numeral express accuracy a[n gauging. More and more many important number  and more accurate gauging which we do.

Rule of writing  important number :

1. All non null numbers are is important number, example : 254 ( 3 IN )

2. All numbers zero laying between non null numbers are important number, example: 5007 ( 4 IN )

3. Zero number to the right of decimal, non null numbers are important number example: 2800 ( 4 IN )

4. Zero number to the right of decimal, non null numbers are not zero is important  numeral, except it has special said the word ( for example under line), example : 3000 ( 3 IN )

5. All numbers to the right of decimal following is important number, example : 4,678 ( 4 IN )

6. It number which is available for written with scientific notation the order is not important number

The rule of important number operation

  1. Addition and subtraction of two important numbers or more result important number that have only one questionable number.
  2. The result of multiplication and division have the important numbers which equals to many important  numbers from the factor which has the least important numbers
  3. If the result number of gauging squared or  rooted  so the result is  number with important number as much as the important number it self.

COMPETENCE TEST  1

1.Here is a union of some units.

1. m2, kg, m, joule

2. newton, joule, volt

3. m3, Js-1, kgms-1

4. kg, ampere, kelvin

Which is not a union of  ….

a.1, 2, 3                                                    d. 4 is just

b.1,3                                                          e. 1, 2, 3, 4

c.2,4

2. Pay attention to magnitude below :

1   Mass, Strength of current, temperature

2   Weigh, force, specific mass

3   Length, amount of matters, intensity of light

4   electric charge, power, energy

The fundamental magnitude union is ….

a.  1, 2, 3                                                 d. 4 is just

b.  1,3                                                      e. 1, 2, 3, 4

c.  2,4

3.  Magnitudes below  group of fundamental magnitudes, except….

a.  length, mass, time                               d. intensity of light, strength of current, temperature

b.  strength of current, time, temperature e. time, length, amount of matters

c.  mass, heavily, wide

4.  Length of wood is 15 m. So-called magnitude at the statement is ….

a.  15                                                      d. length

b.  m                                                       e. timber

c.  15 m

5.  Besaranbesaran hereunder which are scalar magnitudes ….

a.  time, temperature, speed

b.  force, displacement, speed

c.  force, distance, speed

d.  time, distance, transfer

e.  temperature, transfer, speed

6.  Which are vector magnitudes hereunder are ….

a.  Force, heavily, speed, acceleration and speed

b.  force, acceleration, Strength of current and mass

c.  acceleration, speed, Force and weight

d.  acceleration, speed, Force, and dissociation energy of diatomic

e.  speed, acceleration, mass, and transfer

7.  Statement be incorrect dimension below is….

a.  Dimension can be used to compile relation between magnitudes

b.  With dimension, an equation which we do not recognizing it forget it, can be checked fast

c.  Fundament magnitudes have specific dimensions recognize. They can stand by them selves

d.  Dimension of the derivative magnitudes dimension of fundamental magnitudes

e.  Dimension of fundamental magnitudes is determined first based on dimensions derivative  magnitudes.

8.  Look at following tables of magnitude, unit and dimension :

No            Magnitude       Unit                  Dimension

1.          Force               kgms-2                   [ M] [ L] [ T] -2

2.         Effort               kgm2s-2                     [  M] [ L]2[ T] -2

3.         Power              kgm2s-3                 [  M] [ L]2[ T] -3

4.        Impulse             kgm2s-1                [  M] [ L]2[ T] -1

The correct connection is ….

a.  1, 2, 3                                                 d. 4 is just

b.  1,3                                                      e. 1, 2, 3, 4

c.  2,4

9.Dimension from impulse is ….

a.  MLT-2                                                            d. M-1lt

b.  ML-1T                                                           e. MLT

c.  MLT-1

10.Look at to slide calipers figure below :

Reading of slide calipers above is….

a.  6,52 cm                                  d. 6,52 mm

b.  6,34 cm                                  e. 6,32 mm

c.  6,32 cm

11.Look at to screw micrometer figure below :

Reading of screw micrometer above is….

a.  4,75 cm                                  d. 4,325 mm

b.  4,25 cm                                  e. 4,25 mm

c.  4,75 mm

12.Gauging result of slide calipers beside is ….

a.  6,5 mm

b.  6,75 mm

c.  6,85 mm

d.  6,5 cm

e.  6,85 cm

13.Gauging result of screw micrometer beside is ….

a.  1,94 mm

b.  1,90 mm

c.  1,85 mm

d.  1,45 mm

e.  1,44 mm

14.Addition result between 25,67 cm and 506,4 cm it is by written important numeral rules is ….

a.  532,00 cm                                          d. 532,1 cm

b.  532,01 cm                                          e. 532,10 cm

c.  532,07 cm

15.Equivalent value by 8000 m is ….

a.  8.10-12 km                                         d. 8.10-6 km

b.  8.10-9 km                                           e. 8.10-3 km

c.  8.10-8 km

16.Cylinder from gauging result of 0,36010 meter. The number of important  numeral which       implied in the gauging result is … important.

a.  2                                                         d. 5

b.  3                                                         e. 6

c.  4

17.An iron plate has the length of 2,5 m and the width of  1,55 m. Width of the plate is…m2.

a.  3,87                                                    d. 3,9

b.  3,875                                                  e. 4,0

c.  3,88

18.Unit of Internal Pressure SI is….

a.  cmHg                                                              d. Pascal

b.  Atmosphere                                        e. Nm2

c.  Toricolli

19.The correct writing of 25 micrometer which very precise is… m.

a.  0,000025                                            d. 25. 10- 6

b.  0,0000025                                          e. 2,5. 10- 5

c.  0,00000025

20.According to prefix rule in SI, writing of ten million meters can be expressed by squared number ….

a.  10 km                                                 d. 10 Tm

b.  10 Mm                                               e. 10.000.000 m

c.  10 Gm

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