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qUANTITY aND Unit                                                                                      Name :………………………

Quantity is something that can be measured and has unit.

Unit is anything serves to compare in a quantity.

In physic quantity is differentiated into two, basic quantity and derivative quantity.

Basic Quantity

Basic quantity is the base to make other quantities.                                        Table 1. basic quantities and their unit in SI

Derivative Quantity

Derivative quantity is quantity whose unit comes from two or more basic quantities. You can see some example of the derivative quantities in the following table.

Table 2. Derivative quantities and their unit in SI

Unit standard in the international system

A unit can be called as standard if when we use it the result will be the same between one person and another. Meanwhile, non standard unit will have different result if it is used by different people.

Table 3. standard and non standard unit in some quantities

Quantities	Non standard unit	Standard unit
Length	Step, cubic, palm rib	Meter
Mass	Pikul	Gram
Time	A while	Sekon
Volume	A glass, bucket	Meter cubic

Standard unit requirements:

International, can be used around the world

Fixed, cannot change in whatever condition

Easy to imitate, easy to be made and copied for every day use

 Length unit satandard

The standard for length unit is standard meter. For the first, the standard of length made from platinum iridium but in 1960 the scientists decided that one meter equals to the wavelength of orange crypton gas to vibrate for 1,650,763.73 times.

 Mass Unit Standard

Mass is the number of substance or materials in a certain object. The mass of an object remains the same, wherever it is. The mass unit in SI is kilogram. The scientists have decided that one kilogram equals to the mass of an iridium platinum cylinder. The mass of one kilogram is almost the same as 1 liter of pure water in the temperature of 4⁰C.

 Time unit standard

Time scientists ware decided that one second is the time needed by the cesium to vibrate for 9,192,631,770 times.

 Unit Conversion

Besides using meter as the length unit, some European countries use other length units, such as inch, yard, feet, and mile. To understand the quantities of the unit, there is s need conversion.

      Length quantity

1 inch = 2.54 cm

1 cm = 0.394 inch

1 feet = 30.5 cm

1 mile = 1.61 km

1 km = 0.621 mile

      Mass Quantity

1 kg = 0.0685 slug

1 atom mass unit = 1.6 x 10^-27 kg

      Time quantity

1 hour = 60 minute

1 minute = 60 second