# Chapter 1 Notes | Physics 1st Year

## “Measurements”

**Index:**

- Introduction to Physics
- Physical Quantities
- International System of Units
- Errors or Uncertainties
- Significant Figures
- Precision and Accuracy
- Assessment of Total Uncertainty in the Final Result
- Dimensions of Physical Quantities

**Key Points:**

- Physics Is The Study of Entire Physical World.
- The Most Basic Quantities That Can Be Used To Describe The Physical World Are Mass, Length And Time. All Other Quantities, Called Derived Quantities, Can be Describe In Terms Of Some Combinations Of The Base Quantities.
- The Internationally Adopted System Of Used By All The Scientists And Almost All The Countries Of The World Is International System (SI) Of Units. It Consists Of Seven Base Units, Two Supplementary Units And A Number Of Derived Units.
- Errors Due To Incorrect Design Or Calibrations Of the Measuring Device Are Called Systematic Errors. Random Errors Are Due to Unknown Causes And Fluctuations In The Quantity Being Measured.
- The Accuracy Of A Measurement Is The Extent To Which Systematic Error Make A Measured Value Differ From its True Value.
- The Accuracy of A measurement Can be Indicated By the Number Of Significant Figures, Or by a Stated Uncertainty
- The Significant Figures Or Digits in a measured Or Calculated Quantity Are Those Digits That Are Known To be Reasonably Reliable.
- The Result of Multiplication Or Division Has No More Significant Figures Than Any Factor in the input data. Round Off your Calculator result to correct number of digits.
- In Case of addition or subtraction the precision of the result can be only as great the least precise term added or subtracted.
- Each basic measurable physical property represented by a specific symbol written within square brackets is called dimension. All other physical quantities can be derived as combinations of the basic dimensions.
- Equation must be dimensionally Consistent. Two Terms can be added only when they have the same dimension.

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