CHAPTER 1
MAIN QUANTITY AND DERIVED QUANTITY
PHYSICS FOR JUNIOR HIGH SCHOOL VII
Something measurable stated in number
(quantitative), for instance: length, mass, time, temperature, etc.
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QUANTITY
MAIN QUANTITY
DERIVED QUANTITY
QUANTITY
MAIN QUANTITY
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Main quantity is a quantity that its unit is determined first, or a quantity that its unit is defined especially based on international conference.
There are 7 main quantities
Quantity Unit Unit Symbol
length Meter M
Mass Kilogram Kg
Time Second S
Electric currency Ampere A
Temperature Kelvin K
Substance Amount Mole Mole
Light Intensity Candela Cd
PHYSICS FOR JUNIOR HIGH SCHOOL VII
DERIVED QUANTITY
Derived quantity is a quantity that can be derived or taken from main quantities
Derived quantities and their units
Quantity Unit Symbol
Area A M2
Volume V M3
Velocity V M/s or m.s–1
Acceleration A M/s2 or m.s–2
Force F Kg.m/s2 or kg.m.s–2
Work W Kg.m2/s2 or kg.m2.s–2
Power P Kg.m2/s3 or kg.m2.s–3
PHYSICS FOR JUNIOR HIGH SCHOOL VII
THE INTERNATIONAL UNIT
THE INTERNATIONAL UNIT OF LENGTHThe unit of length is meter 1 meter = The space of two scratches on standard meter bar that is made of the compound of platinum-iridium. It is kept in the International Bureau of Weights and Measures (Sevres, Frances)
on November in1983, the definition of meter standard was changed, it was determined that 1 meter is the travelled distance of light (in vacuum) in duration of 1/299.792.458 second
PHYSICS FOR JUNIOR HIGH SCHOOL VII
THE INTERNATIONAL UNIT
THE INTERNATIONAL UNIT OF MASS
The standard unit of mass is kilogram, which means the mass of a platinum-iridium cylinder that is kept in Bureau of Weights and Measures (Sevres, France). The international derived mass standard for U.S.A called prototype kilogram Number 20, kept in a dome in Bureau of National Standard
The standard kilogram number 20 that is kept in the bureau of national standard of U.S.A is a platinum cylinder, kept under the two bell-shaped glass domes (Sources: Serway and Jewett, Physics for Scientists and Engineers, 6th edition, 2004)
PHYSICS FOR JUNIOR HIGH SCHOOL VII
INTERNATIONAL UNIT
INTERNATIONAL UNIT OF TIME
The standard for time is second (s). 1 second is defined as the duration that is needed by cesium atom-133 for vibrating 9.192.631.770 times in transition between two energy level in its basic energy
PHYSICS FOR JUNIOR HIGH SCHOOL VII
UNIT CONVERSION
UNIT CONVERTION OF LENGTH, MASS, AND TIME
Unit Conversion of length and Mass
1. 2,5 km = ... m2. 1.500 cm = ... m3. 2.000 g = ... kg4. 4,25 g = ... mg
ExampleConvert the following units !
answer :1. 2,5 km = 2,5 × 1.000 m = 2.500
m2. 1.500 cm = 1.500 × 1/100 m = 15 m3. 2.000 g = 2.000 × 1/1.000 kg = 2 kg4. 4,25 g = 4,25 × 1.000 mg = 4.250
mg
PHYSICS FOR JUNIOR HIGH SCHOOL VII
UNIT CONVERSION
Unit conversion of time
ExampleConvert the following units !
1. 1,5 hours = ... minutes2. 360 seconds = ... minutes
1. 1,5 hours = 1,5 × 60 minutes = 90 minutes2. 360 seconds = 360 × 1/60 minutes = 6 minutes
Answer :
1 hour = 60 minutes or 1 minute = 1/60 hour
1 minute = 60 seconds or 1 seconds = 1/60 minute
1 hour = 3.600 seconds or 1 second = 1/3.600 hour
PHYSICS FOR JUNIOR HIGH SCHOOL VII
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