BAB 1

Bab 1

Quantity, Unit, and Measurement

1. Quantities

a. Base Quantities

    Characteristic :

• They are not derivations of other quantities.
• They can produce or derive other quantities.

        Base Quantities and Function

• Length (L) = To express the length, width, etc. (metre (m))
• Mass (M) = To express mass of an object (kilogram (kg))
• Time (T) = To express time duration of an event (second (S))
• Electric current (I) = To express the strength of electric current (ampere)
• Temperature = To express the warmness of things (kelvin)
• Light intensity (J) = To express the brightness of light irradiation (candela)
• Amount of substance (N) = To express the amount of particles composing things (mol)

b. Derived Quantities

    Definition : All physical quantities except the base quantities

    Example : Volume, mass density, velocity, etc.

    volume = combination of length, length, and length

    mass density = combination of  mass, length, length, and length

    velocity = combination of length and time

c. Measurement

    Definition = is the comparison of the magnitude of quantity with the value of measuring devices

2. Units

a. S1 units

Base quantities	Unit	Abbreviation
Length	Meter	M
Mass	Kilogram	Kg
Time	Second	S
Electric Current	Ampere	A
Temperature	Kelvin	K
Light intensity	Candela	Cd
Amount of substance	mole	Mol

b. Derived S1

    Because derived quantities are combination of base quantities, the units of the derived quantities are combinations of units of the corresponding base quantities. For example : unit of velocity=m/s

c. Prefixes of units

Prefixes	Symbols	Multiplication Factors
	More than One
Kilo	K	10^3
Mega	M	10^6
Giga	G	10^9
Tera	T	10^12
Peta	P	10^15
exa	E	10^18

	Less than one
Milli	m	10^-3
Micro	Micro	10^-6
Nano	n	10^-9
Piko	p	10^-12
Femto	f	10^-15
Atto	a	10^-18

	Other frequently used prefixes
Deci	d	10^-1
Centi	c	10^-2
angstrom	A	10^-12

2. Measurement

·         Measuring is the process to know the quantities of the object in standard units

·         The tools are ruler, vernier caliper, micro meter

a.       Ruler

Smallest scale = mm (1 mm)

Uncertainty : ½ smallest scale (05 mm)

Precision : same calculation and uncertainty

b.      Vernier Caliper

Smallest scale : 0.1 mm

Uncertainty : ½ smallest scale (0.05Precision : same calculation with Uncertainty

Contuns base scale and nonius scale

c.       Micro meter

Smallest scale : 0.01 mm

Uncertainty : ½ x 0.01 : 0.005 mm

Precision : ½ x 0.01 : 0.005 mm

·         Factors are different tools or device, human error, environment , factor superstition

·         Report the measurement result :

              X=Xoriginal +/-  deltaX

              Xoriginal : calculation result

              Delta x : Uncertainty

·         Current measurement result

3. Dimension

Base Quantity	Dimension
Length	(L)
Mass	(M)
Time	(T)
Current	(I)
Temperature	(Teta)
Light intensity	(J)
Number of substance	(N)

Example :

·         3 kg + 2 N = 3.2 Kg

      (M) + (M) . (L) (T)^-2

      (M)^2(L)(T)

·         (v) = (s)/(t) = (L)/(t) = (L)(T)^-1

·         (a) = (v)/(t) = (L)(T)^-1/(T) = (L)(T)^-2

4. Significant figure

Rules :

  Ø  All non zero digits are considered significant

Ex : 91 has two significant figure

        12345 has five significant figure

  Ø  Zeros appearing anywhere between two non-zero digits are significant

Ex : 104.2356 has seven significant figures

  Ø  All number in scientific notation are scientific figures 

  Ø  Leading zero are not significant figure

Ex : 0.00000236 has 3 significant figures.

  Ø  Trailing zero in a number containing a decimal point are significant.

Ex : 13.2500 has six significant figures

        0.0000125600 still has six significant figures

        150.00 has five significant figures since it has three trailing zero.

Multiplication and Division

0.628 cm x 2.2 cm = 1.38226 cm^2

                                = 1.4 cm^2 (2 sf)

4.554 x 105 kg : 3.00 x 10^2 kg = 1.5718 x 10^5-2

                                                     = 1.52 10^3 (3 sf)