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Questions and Answers
What is the metric system based on?
What is the modern metric system of measurement called?
In which year was the International System of Units (SI) established?
What is the base unit of length in the MKS System?
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What are the three systems of units?
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What are the two parts of a measurement?
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What is the SI unit of thermodynamic temperature?
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What is the SI unit of electric current?
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What is the SI unit of mass?
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What is the SI unit of luminous intensity?
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What is the SI unit of length?
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What is the SI unit of amount of substance?
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What is the unit of pressure that equals the average air pressure at sea level?
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What is the dimension of the metric unit of pressure?
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What is the equivalent pressure in pascal if we have a pressure of 1 atmosphere?
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What is the unit of pressure that is commonly used in engineering applications?
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What is the relation between pascal and atmosphere?
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How many pascals are there in 1 atmosphere?
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Study Notes
SI Base Units
- MKS System: Meter (m) for length, kilogram (kg) for mass, second (s) for time.
- CGS System: Centimeter (cm) for length, gram (g) for mass, second (s) for time.
- Base Quantities: Include electric current (ampere, A), thermodynamic temperature (Kelvin, K), amount of substance (mole, mol), luminous intensity (candela, cd).
Accuracy, Precision, and Errors
- Measurement Error: Every measurement contains some uncertainty, referred to as error.
- Accuracy: Proximity of a measured value to the true value.
- Precision: Resolution or limit of measurement, indicating consistency over repeated trials.
Types of Measurement Errors
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Systematic Errors:
- Caused by instrumental flaws (calibration issues), technique imperfections, or personal biases.
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Random Errors:
- Result from unpredictable fluctuations (temperature, voltage changes) and unbiased observer discrepancies.
Measurements and Units
- Measurement Definition: Comparison of a physical quantity to a known standard.
- Magnitude and Units: Any measurement consists of a magnitude and the unit (e.g., 5 meters).
- SI System: Modern metric system established in 1960, consisting of decimal-based units.
Pressure Measurement
- Pressure Formula: ( p = \frac{F}{A} )
-
Units of Pressure: Pascal (Pa, where 1 Pa = 1 N/m²), pounds per square foot (lb/ft²), pounds per square inch (psi), millimeters of mercury (mm Hg), inches of mercury (in Hg), atmosphere (atm).
- Atmospheric Pressure: 1 atm = ( 1.01 \times 10^5 ) Pa = 14.7 psi.
Example Problem - Volume and Mass of Water
- Pool Dimensions: 15 m wide, 40 m long, 6 m deep.
- Volume Calculation: Volume = ( 15 \times 40 \times 6 = 3600 , m³ ).
- Mass of Water: Using density ( \rho = 1000 , kg/m³ ), mass = ( \rho \times V = 1000 \times 3600 = 3.6 \times 10^6 , kg ).
Periodic Motion and Simple Harmonic Motion
- Periodic Motion: Defined as motion that repeats over time, examples include swings and pendulums.
- Simple Harmonic Motion: A specific type of periodic motion with a constant oscillation time known as the period (T).
- Period (T): Time taken to complete one oscillation, measured in seconds or other convenient time units.
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Description
Learn about the basics of measurements and units in physics, including accuracy and precision of instruments, and errors in measurement. Understand how to compare physical quantities with standard units.
