Podcast
Questions and Answers
Which of the following systems is known as the metric system?
Which of the following systems is known as the metric system?
What is the boiling point of water on the Fahrenheit scale?
What is the boiling point of water on the Fahrenheit scale?
212 °F
What is the unit of power defined by James Watt?
What is the unit of power defined by James Watt?
Horsepower
The SI unit for temperature is the ______.
The SI unit for temperature is the ______.
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The United States customary system was established in 1832.
The United States customary system was established in 1832.
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What is the value of the speed of light in meters per second?
What is the value of the speed of light in meters per second?
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Match the following SI base units with their quantities:
Match the following SI base units with their quantities:
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What is the defining constant for the kilogram?
What is the defining constant for the kilogram?
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What is the relationship between Mechanical Horsepower and Watts?
What is the relationship between Mechanical Horsepower and Watts?
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Which of the following temperatures represents human body temperature in Fahrenheit?
Which of the following temperatures represents human body temperature in Fahrenheit?
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Study Notes
Units Overview
- Units are fundamental for measurements and calculations in science and engineering.
- Various systems of units include:
- Metric system (established in France, 1795)
- CGS (centimeter-gram-second)
- MTS (metre-tonne-second)
- MKS (metre-kilogram-second)
- MMGS (millimeter-gram-second)
- English system (pre-1824)
- Imperial units (post-1824)
- US customary system (1832)
- International System of Units (SI units) introduced in 1960, comprises 7 base units and derived units.
Temperature Scales
-
Fahrenheit scale developed by Daniel Gabriel Fahrenheit in 1724.
- Boiling point of water: 212 °F
- Freezing point of water: 32 °F
- Human body temperature: 96 °F (average 98.6 °F)
- 0 °F represents a mixture of ice, water, and ammonium chloride.
-
Celsius scale established by Anders Celsius in 1742.
-
Absolute temperature scale proposed by Lord Kelvin in 1848.
Power Measurement
-
Horsepower defined by James Watt in 1782.
- Capable of rotating a 12 m mill wheel 144 times per hour with a force of 180 pounds-force.
- 1 Mechanical Horsepower equals 745.7 W.
-
Watt defined in 1882 as:
- 1 W = 1 Joule/second = 1 Newton-meter/second = 1 kg·m²/s³ = 1 V·A.
SI Units Overview
- 7 SI base units with defined constants:
- Time: second (s) defined by transition frequency (ΔνCs) = 9,192,631,770 Hz.
- Length: metre (m) defined by speed of light (c) = 299,792,458 m/s.
- Mass: kilogram (kg) defined by Planck constant (h) = 6.62607015×10⁻³⁴ J·s.
- Electric current: ampere (A) defined by elementary charge (e) = 1.602176634×10⁻¹⁹ C.
- Thermodynamic temperature: kelvin (K) defined by Boltzmann constant (k) = 1.380649×10⁻²³ J/K.
- Amount of substance: mole (mol) defined by Avogadro constant (Nₐ) = 6.02214076×10²³ mol⁻¹.
- Luminous intensity: candela (cd) related to luminous efficacy of radiation at 540 THz = 683 lm/W.
Redefinition of SI Units (2019)
- Major updates to the definitions of SI base units to enhance consistency and precision.
- Re-definition links the units to fixed numerical values of fundamental constants.
Dimensions
- Dimensions represent general physical quantities and are independent of any specific unit.
- Understanding dimensions is essential for interpreting physical laws and relationships between different quantities.
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Description
Test your understanding of units and dimensions in various measurement systems. This quiz covers the metric system, CGS, MTS, and more. Refresh your knowledge on how these systems form the basis for calculations in scientific contexts.
