Table of contents | |
Physical Quantity | |
System of Units | |
Fundamental Quantities | |
Derived Quantities |
A physical quantity is a property of a body, substance, or phenomenon that can be quantified through measurement.
Measurement of a Physical Quantity
Measurement involves assigning a value to a physical quantity by comparing it with a standard or calibrated unit of that quantity. To determine the value or magnitude of a physical quantity, it is typically measured using different systems of units.
Errors in Measurement:
An error in measurement is the difference between the true value and the measured value of a quantity. There are three main types of measurement errors:
Physical quantities are measured using four main systems of units:
Fundamental quantities are those that are independent of each other, and their units are called fundamental units. The most widely accepted system is the SI system, adopted in 1971 by the Conference of Weights and Measures held in Geneva. There are seven fundamental quantities in the SI system, along with two supplementary fundamental units:
Derived quantities are those obtained using fundamental quantities, and their units are called derived units. Examples include velocity, force, work, density, and momentum.
Unit of Length
The SI unit of length is the metre (m). One metre is the distance light travels in a vacuum in 1/299,792,458 of a second.
Other Units of Length
Area is related to the square of length. Some units of area include:
Volume is related to the cube of length. Some units of volume include:
The SI unit of mass is the kilogram (kg). One kilogram is defined as the mass of 5.0188 × 1025 atoms of carbon-12.
Other Units of Mass:
The SI unit of time is the second. One second is defined as 1/86,400 of a mean solar day.
Other Units of Time:
Important Prefixes to Units
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1. What are fundamental quantities in the system of units? |
2. Can derived quantities be expressed in terms of fundamental quantities? |
3. How are physical quantities measured in the system of units? |
4. What are some examples of derived quantities in the system of units? |
5. Why is it important to use a standardized system of units in scientific measurements? |
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