فیزیک و اندازه گیری

• The OCR text is notes about physics and measurements.
• The notes include sections about the nature of physics as a science, measurement, units, and related subjects.

Physics: The Basic Science

• Physics encompasses the study of both living and non-living things
• Biology includes zoology and botany
• Physics is fundamental, covering the basic aspects of nature like motion, forces, energy, matter, heat, sound, and light
• Chemistry studies atoms and their combinations into molecules
• Biology relies on chemistry, which in turn relies on physics, establishing physics as the most fundamental science

Science and Technology

• Science gathers and organizes information, while technology applies this knowledge for practical purposes and provides tools for further exploration
• Technology can be both beneficial and harmful e.g. extraction and burning of fossil fuels for energy
• Assigning blame for problems like pollution to technology is unreasonable, it's how humans use it that matters

Importance of Measurement

• Measurement is essential for scientific understanding
• Kelvin emphasized that quantifying something is key to understanding it

Physical Quantities

• Physical quantities are used to study physical phenomena quantitatively
• Fundamental quantities can be measured directly e.g. time, length, and mass
• Derived quantities are measured indirectly, using relationships between quantities e.g. speed

Scalar and Vector Quantities

• Scalar quantities are fully defined by a number and a unit e.g. mass, time, and volume
• Vector quantities require both a magnitude and a direction for complete specification e.g. displacement, velocity, acceleration, and force

International System of Units (SI)

• The SI system provides a standard for measurements, ensuring global consistency
• It is also known as the modern metric system
• SI units facilitate communication and trade
• It defines specific quantities as base units and derives others from them

SI Base Units

• Length - meter (m)
• Mass - kilogram (kg)
• Time - second (s)
• Electric Current - Ampere (A)
• Temperature - Kelvin (K)
• Amount of Substance - mole (mol)
• Luminous Intensity - candela (cd)

Standards of Length, Mass and Time

• Meter is defined as the distance light travels in a specific fraction of a second
• Kilogram is the SI unit of mass, based on a platinum-iridium cylinder
• Second is the SI unit of time

Applying Measurement

• Use appropriate units according to the length
• For large distances use kilometers, for small e.g. millimeters
• Converting between units is a common task
• Older units include ' ذرع' and ' فرسنگ'

Errors and Precision in Measurement

• Measurements always have inherent errors
• Using precise instruments and methods can minimize error, but not eliminate it
• Precision is limited by the instrument's scale division
• Digital instruments has error equal to one unit of the last digit

Significant Figures

• Record numbers with appropriate level of significance
• Include a best guess in the report
• In multiplication and division the number of significant figures is equal to number of significant figures in least precisely known value

Scientific Notation

• An easy way to represent very large numbers
• Easily move decimal to where you want and multiply the remaining digits by an exponent
• Example
  • 300000 can be written as 3x10^5

Changing Units

• Converting a unit into the unit we desire
• This can be done using using chain conversion
• Example
  • 1/min equals 60 seconds
  • 5min can be expressed with this conversion 5min=300sec

Other notes

• One liter equals one cubic decimeter
• Newton's second law equation F=am helps in figuring out relationships between quantities

Density

• Density is mass per unit volume, denoted by ρ
• Formula for density: ρ = m/V
• Units for Density is kg/m3