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Questions and Answers
What is the Planck constant related to in the definition of the kilogram?
What is the Planck constant related to in the definition of the kilogram?
What is the least count of a Vernier Calipers?
What is the least count of a Vernier Calipers?
What is the formula for relative error?
What is the formula for relative error?
What is the unit of length that is equivalent to 5 meters?
What is the unit of length that is equivalent to 5 meters?
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What is the primary purpose of dimensional analysis?
What is the primary purpose of dimensional analysis?
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What is the difference between fundamental and derived units?
What is the difference between fundamental and derived units?
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What is the term for the closeness of a measured value to the true value?
What is the term for the closeness of a measured value to the true value?
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What is the definition of significant figures?
What is the definition of significant figures?
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What is the SI unit of electric current?
What is the SI unit of electric current?
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Study Notes
Units and Measurement
- A physical quantity is a quantity that can be measured and expressed in terms of a number and a unit.
- Measurement is the process of comparing an unknown quantity with a known standard (unit).
Fundamental and Derived Units
- Fundamental units are basic units for fundamental quantities, such as meter for length, kilogram for mass, and second for time.
- Derived units are units derived from fundamental units, such as m/s for velocity and N for force.
System of Units
- The International System of Units (SI) is the modern form of the metric system and the most widely used system of measurement.
- SI units include:
- Meter (m) for length
- Kilogram (kg) for mass
- Second (s) for time
- Ampere (A) for electric current
- Kelvin (K) for temperature
- Mole (mol) for amount of substance
- Candela (cd) for luminous intensity
Accuracy, Precision, and Errors in Measurement
- Accuracy refers to the closeness of a measured value to the true value.
- Precision refers to the closeness of repeated measurements to each other.
- Errors can be classified into two types:
- Systematic errors: consistent and predictable errors due to faulty equipment or bias.
- Random errors: errors due to unknown and unpredictable variations.
Significant Figures
- Significant figures are digits in a measurement that are known reliably plus one last digit that is estimated.
- Rules for significant figures:
- All non-zero digits are significant.
- Zeros between significant figures are significant.
- Leading zeros are not significant.
- Trailing zeros are significant if there is a decimal point.
Dimensional Analysis
- Dimension is the nature of a physical quantity expressed in terms of fundamental quantities, such as [L] for length and [M] for mass.
- Dimensional formula is an expression showing how and which of the fundamental units are involved, such as [M L T^-2] for force.
- Applications of dimensional analysis:
- Checking the correctness of equations.
- Converting units from one system to another.
Standard Units and Measurements
- Meter is defined as the length of the path traveled by light in vacuum during a time interval of 1/299,792,458 seconds.
- Kilogram is defined by the Planck constant, where h = 6.62607015 × 10^-34 Js.
- Second is defined as the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium-133 atom.
Measuring Instruments
- Vernier calipers measure length with a least count of 0.01 cm.
- Micrometer screw gauge measures small lengths with a least count of 0.01 mm.
Errors in Measurements
- Absolute error is the difference between the true value and the measured value.
- Relative error is the absolute error divided by the true value.
- Percentage error is the relative error expressed in percentage.
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Description
Learn about physical quantities, measurement, fundamental units, and derived units in this quiz. Understand the basics of unit conversion and measurement systems.
