In this section we have lean in many fields

- Physical quantities and units
- Dimensions
- Measuring instruments
- Scalars and vectors

### 1-Measurement

Measurement is indispensable. It is getting close to our lives. We need it to declare the identity of something. For example, your height, weight, and age. We need Measurement to declare our identity. We can not say where there is no measurement. Technology has improved through measurements.

There are a size and a unit in a measurement. A various physical instrument is required to measure various Physical constituents. For example, the meter ruler to measure the length, the weight balance to measure the weight, the stopwatch to measure the time.

Let’s see how the measurements have gone far. The smallest length is the radius of the atomic nucleus. The largest length is the end of the universe. We have to measure from this smallest to the highest value.

Next, we see the time. The smallest time is the time to light through the atomic nucleus. The greatest time is the age of the universe. We have to measure the time from this smallest to the highest value.

Next, talk about mass. The smallest mass is the electron mass. The largest mass will be the mass of a galaxy. We have to measure this same as above. We never go out of these ranges. It’s really wonderful. There is nothing to find anything out of this range.

Many countries have used different types of units in ancient times. For example, the British unit system. CGS units. The use of different types of units has caused international problems. Such as sharing our knowledge with others and trading with other countries. For this reason, each country decided at a convention in Geneva in 1960 to use the same unit method. This unit is known as the “System International d’ Unit’s – SI “. Today we are using this unit system.

### Physical quantity

If some value is measured in a physical system, it is known as a physical quantity. There are seven basic units used for measuring physical constants. They can be characterized as the length, mass, time, electric current, thermal temperature, luminous intensity and amount of substances.

### The following are the constraints, units, and symbols given in the table below.

Basic (fundamental) Quantities | Unit | Symbol | |
---|---|---|---|

1 | Mass | kilogram | kg |

2 | Length | metre | m |

3 | Time | second | s |

4 | Electric current | Ampere | A |

5 | Thermodynamic temperature | Kelvin | K |

6 | Luminous Intensity | candela | cd |

7 | Amount of substance | mole | mol |

Two supplementary | Plane angle Solid angle | radian steradian | rad sr |

### Derived quantities

The Derived quantities that can be expressed in terms of fundamental physical quantities are derived from the initial quantities.

The following are some of the most commonly derived bases of derivatives.

Quantities | Symbol | Name |
---|---|---|

Force | N | newton |

Pressure | Pa | pascal |

Energy, Work | J | joule |

Power | W | watt |

Frequency | Hz | hertz |

Electric Charge | C | coulomb |

Electromotive force | V | volt |

Electrical Resistance | Ω | ohm |

Electrical Conductance | S | Siemen |

Permeability | H | Henry |

Capacity | F | farad |

Magnetic flux | Wb | Weber |

Magnetic flux density | T | Tesla |

There are so many units available and you will be able to study in your next lessons.

### Prefixes

When the physical quantities are too small or too large to be written and read it is not easy. In such cases, prefixes are used.

Multiplier factor | The name of the prefix | Symbol |
---|---|---|

10^{18} | Exa | E |

10^{15} | Peta | P |

10^{12} | Tera | T |

10^{9} | Giga | G |

10^{6} | Mega | M |

10^{3} | Kilo | kg |

10^{2} | hecto | h |

10^{1} | deca | da |

10^{-1} | deci | d |

10^{-2} | centi | c |

10^{-3} | milli | m |

10^{-6} | micro | µ |

10^{-9} | nano | n |

10^{-12} | pico | p |

10^{-15} | femto | f |

10^{-18} | atto | a |

### How to apply the prefix to the SI unit

The prefix should be in front of the SI unit.There should not be a gap between the prefix and the unit.

Examples … cm, mm, km, KN

### Dimensions

Dimension is only a symbol, not a unit. It is a symbol of a Basic physical quantity. They can be **L** for the length, **M** for the mass and **T** for the time.When writing this, capital letters should be used in the English alphabet.

**Following are the dimensions of some of the physical constituents we encounter:**

Physical volume | Definition | Dimensions |
---|---|---|

Area | Length * width | L^{2} |

Volume | Length * width * height | L^{3} |

Density | Mass / volume | ML^{-3} |

Velocity | Displacement rate of displacement | LT^{-1} |

Acceleration | Speed of change of velocity | kgm^{-3} |

Force | Mass * Acceleration | MLT^{-2} |

Now you can find the dimensions of **other** physical quantities. This is found in the basic definition of physical constituents or by the equation.

There also Physical constituents which have no dimensions. They are the reference number, the friction coefficient. There also physical quantities which have no dimensions but they have units. They are the flat angle, the solid angle and … etc.

## Benefits of dimensions

- The truth of a relationship given to a physical constellation can be tested
- A relationship can be derived from a physical constituent.
- We can recognize unknown physical set in a given relationship between physical quantities.

Gain analysis can only be done using a variable number of 3 or less

We assume the physical constituents a, b, c, d, and e are connected as a = bc + d / e. It is to be corrected by the dimensions It should be [a] = [bc] = [d/e] . The display in [x] in the parentheses refers to the x’s dimension.

Let’s go to the next lesson. By studying these lessons you can get very good results.Click here to the Next

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