Measurements

MEASUREMENTS

Page 3: Definition of Measurement

  • Measurement is defined as the determining of the extent, dimensions, quantity or capacity of matter by means of a standard.

Page 4: Systems of Measurement

1. Metric System

  • The metric system is the commonly used method of measurement.

  • It is best described using:

    • MKS: Meter-Kilogram-Second

    • CGS: Centimeter-Gram-Second

  • Both MKS and CGS are now part of the SI (Système International d'Unités), which is the modified metric system.

2. English System

  • Also known as the British System of Measurement; it is commonly used in English-speaking countries, particularly in the United Kingdom.

  • Standard Units:

    • Length: Foot

    • Mass: Pound

    • Time: Second

  • Conversions within this system are considered complicated compared to the metric system, requiring memorization of numerous conversion factors for a given physical quantity.

Page 5: Quantities and Types

  • Quantity: A part or portion of a thing that can be measured.

Basic Types of Quantity

  1. Fundamental Quantities

    • Referred to as basic quantities.

  2. Derived Quantities

    • These are combinations of any of the fundamental quantities.

Page 6: Fundamental/Base Units

Following are the official definitions of the seven fundamental/base units, as given by the International Bureau of Weights and Measures (BIPM):

  • Meter (m): Distance

    • "The metre is the length of the path travelled by light in vacuum during a time interval of 1/299 792 458 of a second."

  • Kilogram (kg): Mass

    • "The kilogram is equal to the mass of the international prototype of the kilogram."

  • Second (s): Time

    • "The second is the duration of 9 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom."

  • Ampere (A): Electric current

    • "The ampere is that constant current which, if maintained in two straight parallel conductors of infinite length, of negligible circular cross-section, and placed 1 metre apart in vacuum, would produce between these conductors a force equal to 2 × 10^{-7} newton per metre of length."

  • Kelvin (K): Temperature

    • "The kelvin is the fraction 1/273.16 of the thermodynamic temperature of the triple point of water."

  • Mole (mol): Amount of substance

    • "The mole is the amount of substance of a system which contains as many elementary entities as there are atoms in 0.012 kilogram of carbon 12. When the mole is used, the elementary entities must be specified and may be atoms, molecules, ions, electrons, other particles, or specified groups of such particles."

  • Candela (cd): Luminous intensity

    • "The candela is the luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency 540 × 10^{12} hertz and that has a radiant intensity in that direction of 1/683 watt per steradian."

Page 7: Factor Names and Symbols

Factors of Measurement Units

Factor

Name

Symbol

10^{9}

giga

G

10^{6}

mega

M

10^{5}

kilo

k

10^{2}

hecto

h

10^{1}

deka

da

10^{-1}

deci

d

10^{-2}

centi

c

10^{-3}

milli

m

10^{-6}

micro

μ

10^{-9}

nano

n

Page 8: Examples of Derived Quantities

SI Units of Derived Quantities

Derived Quantity

SI Unit

Area

square meter, m²

Volume

cubic meter, m³

Density

kilogram/cubic meter, kg/m³

Speed (Velocity)

meter/second, m/s

Acceleration

meter/square second, m/s²

Pressure

Pascal, N/m²

Power

Watt, W

Electric Field

Volt, V/m

Page 9: Conversion of Units

Unit Conversion Techniques

  • The representation of every quantity with corresponding units can often be converted into its equivalent unit. This is especially useful in scientific research or when measuring the properties or dimensions of an object.

1. From Large to Small Units

  • To convert from a large to a small unit, multiply the given number of the large unit by the number of small units contained in one large unit.

2. From Small to Large Units

  • To convert from a small to a large unit, divide the given number of the small unit by the number of small units contained in one large unit.

Page 10: Benefits of Metrication

  1. Easier Learning: The metric system (SI) is much easier to learn, remember, and apply.

    • If universally adopted, it eliminates the need to memorize conversion factors between English and Metric units.

  2. Simplified Calculations: Calculations are simpler in the metric system.

    • The use of metric units allows for easier derivation of larger and smaller units through powers of 10.

  3. Uniformity in Measurement: The global agreement on the metric system enhances scientific communication and facilitates the development and practice of science professions.