SI Units - Revision history

David1248y at 08:02, 29 November 2025

2025-11-29T08:02:55Z

← Older revision		Revision as of 04:02, 29 November 2025
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	This page describes the International System of Units and lists its units.		This page describes the International System of Units and lists its units.

			Recently Edited by DAVID SHIN
	==The Main Idea==		==The Main Idea==

David1248y: /* Unit Conversion */

2025-11-29T08:01:18Z

Unit Conversion

← Older revision		Revision as of 04:01, 29 November 2025
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	Finally, it is worth noting that when converting between higher powers of units, such as cubic inches to cubic cm, their conversion factors are raised to that power also. That is, one inch is equivalent to 2.54 cm, so one cubic inch is equivalent to 2.54<sup>3</sup> = 16.39 cubic cm.		Finally, it is worth noting that when converting between higher powers of units, such as cubic inches to cubic cm, their conversion factors are raised to that power also. That is, one inch is equivalent to 2.54 cm, so one cubic inch is equivalent to 2.54<sup>3</sup> = 16.39 cubic cm.

	Below is an example of dimensional analysis within Glowscript to convert from inches to meters. You divide inches by 12 and 3.281 as there are 12 inches per foot, and 3.281 feet per meter.		Below is an example of dimensional analysis within Glowscript to convert from inches to meters. You divide inches by 12 and 3.281 as there are 12 inches per foot, and 3.281 feet per meter.

	~~<iframe> src="~~https://www.glowscript.org/#/user/david.shin/folder/MyPrograms/program/webpage/edit~~" width="auto" height="400"></iframe>~~		https://www.glowscript.org/#/user/david.shin/folder/MyPrograms/program/webpage/edit

	==Examples==		==Examples==

David1248y: /* Unit Conversion */

2025-11-29T07:59:19Z

Unit Conversion

← Older revision		Revision as of 03:59, 29 November 2025
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	Below is an example of dimensional analysis within Glowscript to convert from inches to meters. You divide inches by 12 and 3.281 as there are 12 inches per foot, and 3.281 feet per meter.		Below is an example of dimensional analysis within Glowscript to convert from inches to meters. You divide inches by 12 and 3.281 as there are 12 inches per foot, and 3.281 feet per meter.

	<iframe src="https://www.glowscript.org/#/user/david.shin/folder/MyPrograms/program/webpage/edit" width="auto" height="400"></iframe>		<iframe> src="https://www.glowscript.org/#/user/david.shin/folder/MyPrograms/program/webpage/edit" width="auto" height="400"></iframe>

	==Examples==		==Examples==

David1248y: /* Unit Conversion */

2025-11-29T04:31:52Z

Unit Conversion

← Older revision		Revision as of 00:31, 29 November 2025
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	Finally, it is worth noting that when converting between higher powers of units, such as cubic inches to cubic cm, their conversion factors are raised to that power also. That is, one inch is equivalent to 2.54 cm, so one cubic inch is equivalent to 2.54<sup>3</sup> = 16.39 cubic cm.		Finally, it is worth noting that when converting between higher powers of units, such as cubic inches to cubic cm, their conversion factors are raised to that power also. That is, one inch is equivalent to 2.54 cm, so one cubic inch is equivalent to 2.54<sup>3</sup> = 16.39 cubic cm.

			Below is an example of dimensional analysis within Glowscript to convert from inches to meters. You divide inches by 12 and 3.281 as there are 12 inches per foot, and 3.281 feet per meter.

			<iframe src="https://www.glowscript.org/#/user/david.shin/folder/MyPrograms/program/webpage/edit" width="auto" height="400"></iframe>

	==Examples==		==Examples==

David1248y at 04:22, 29 November 2025

2025-11-29T04:22:44Z

← Older revision		Revision as of 00:22, 29 November 2025
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	For the ideal gas law to be numerically true, the ideal gas constant <math>R</math> must be in the correct units. The SI units for pressure, volume, and temperature respectively are the kilopascal (kPa), the cubic meter (m<sup>3</sup>), and Kelvin (K). If these units are used, <math>R</math> must be given in m<sup>3</sup> kPa / mol K. That way, both sides of the equation are in m<sup>3</sup> kPa. R can also be given in other units, as long as they are a unit of volume times a unit of pressure divided by moles and a unit of temperature. Its value depends on the units used. In fact, all natural constants can have different values depending on the units in which they are given. In this class, they are typically given in their SI units.		For the ideal gas law to be numerically true, the ideal gas constant <math>R</math> must be in the correct units. The SI units for pressure, volume, and temperature respectively are the kilopascal (kPa), the cubic meter (m<sup>3</sup>), and Kelvin (K). If these units are used, <math>R</math> must be given in m<sup>3</sup> kPa / mol K. That way, both sides of the equation are in m<sup>3</sup> kPa. R can also be given in other units, as long as they are a unit of volume times a unit of pressure divided by moles and a unit of temperature. Its value depends on the units used. In fact, all natural constants can have different values depending on the units in which they are given. In this class, they are typically given in their SI units.

	All equations in physics, like <math>PV=nRT</math>, are true for all units, as long as their two sides agree in units, which requires the correct versions of any natural constants. Generally, SI units are preferred.		All equations in physics, like <math>PV=nRT</math>, are true for all units, as long as their two sides agree in units, which requires the correct versions of any natural constants. Generally, SI units are preferred. For example, the general force equation <math>F = ma</math> and the force gravity equation <math>F = mg</math> display that both sides equal Newtons, or kg(m/s^2) which are the units of m and a/g respectively.

	The fact that both sides of an equation must have the same units can be useful for determining the units of a quantity, or, if the units of all quantities are known, for verifying that a derived equation makes sense and is possible.		The fact that both sides of an equation must have the same units can be useful for determining the units of a quantity, or, if the units of all quantities are known, for verifying that a derived equation makes sense and is possible.

David1248y at 03:33, 29 November 2025

2025-11-29T03:33:31Z

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	The International System of Units is adaptable and can change over time to meet the evolving needs of scientists. Over the last several centuries, the number of base units has grown from 3 to 7 as a result of the discovery of new dimensions that could not be expressed in terms of existing base units. The number of derived units recognized as meaningful has also grown substantially and will likely continue to as the human understanding of the physical world improves. Additionally, the seven base units have undergone redefinition at several points in time, most recently on May 20 2019. The purpose of each redefinition is not to change the units' values (in fact, their values are changed as little as possible), but to make their definitions more universally constant and reproducible.		The International System of Units is adaptable and can change over time to meet the evolving needs of scientists. Over the last several centuries, the number of base units has grown from 3 to 7 as a result of the discovery of new dimensions that could not be expressed in terms of existing base units. The number of derived units recognized as meaningful has also grown substantially and will likely continue to as the human understanding of the physical world improves. Additionally, the seven base units have undergone redefinition at several points in time, most recently on May 20 2019. The purpose of each redefinition is not to change the units' values (in fact, their values are changed as little as possible), but to make their definitions more universally constant and reproducible.

			SI units are important because they provide a consistent, universally accepted framework for making and comparing measurements, which is essential for clear communication in science, engineering, and everyday life. By ensuring that all researchers and professionals use the same standardized units, the SI system eliminates confusion, reduces errors, and allows experiments and calculations to be replicated anywhere in the world - providing a strong translational framework for computational work. This consistency is especially crucial in global collaboration, manufacturing, medicine, and technology, where even small discrepancies in units can lead to major mistakes. Their adaptability and precision make SI units the foundation upon which modern scientific understanding continues to grow.

	===The Seven Base Units===		===The Seven Base Units===

Jnation8 at 17:10, 29 November 2021

2021-11-29T17:10:25Z

← Older revision		Revision as of 13:10, 29 November 2021
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	This page describes the International System of Units and lists its units.		This page describes the International System of Units and lists its units.

	~~'''Claimed By: Jared Nation'''~~
	==The Main Idea==		==The Main Idea==

Jnation8 at 17:08, 29 November 2021

2021-11-29T17:08:41Z

← Older revision		Revision as of 13:08, 29 November 2021
Line 1:		Line 1:
	This page describes the International System of Units and lists its units.		This page describes the International System of Units and lists its units.

	'''Claimed By: Jared Nation'''		'''Claimed By: Jared Nation'''
	==The Main Idea==		==The Main Idea==

Jnation8 at 17:08, 29 November 2021

2021-11-29T17:08:19Z

← Older revision		Revision as of 13:08, 29 November 2021
Line 1:		Line 1:
	This page describes the International System of Units and lists its units.		This page describes the International System of Units and lists its units.
			'''Claimed By: Jared Nation'''
	==The Main Idea==		==The Main Idea==

YorickAndeweg: /* Kilogram (kg) */

2019-08-16T21:52:00Z

Kilogram (kg)

← Older revision		Revision as of 17:52, 16 August 2019
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	The kilogram measures mass.		The kilogram measures mass.

	Today, the kilogram is defined by fixing the value of Planck's constant <math>h</math> at exactly 6.62607015×10−34 J s. Recall that the joule is not a base unit, but a derived unit equal to the kg m<sup>2</sup>/s<sup>2</sup>. Since the meter and the second are already defined, this leaves only one possible value for the kilogram. This definition was instated as part of the SI unit redefinition of May 20, 2019. [https://www.youtube.com/watch?v=c_e1wITe_ig&t=521s This video] by the science YouTube channel Veritasium describes the redefinition of base units of May 20, 2019.		Today, the kilogram is defined by fixing the value of Planck's constant <math>h</math> at exactly 6.62607015×10−34 J s. Recall that the joule is not a base unit, but a derived unit equal to the kg m<sup>2</sup>/s<sup>2</sup>. Since the meter and the second are already defined, this leaves only one possible value for the kilogram. This definition was instated as part of the SI unit redefinition of May 20, 2019. [https://www.youtube.com/watch?v=c_e1wITe_ig&t=521s This video] by the science YouTube channel Veritasium describes the redefinition of base units of May 20, 2019, with an emphasis on the new definition of the kilogram.

	In 1973, the SI unit for mass was called the grave. It was defined as being the mass of 1 liter of pure water at its freezing temperature. The grave was renamed to the kilogram, and later, in 1889, it was redefined as the mass of a specific sample of a platinum alloy. The sample is called "Le Grand K" and is kept in a humidity-controlled vault just outside of Paris, France. This definition was inadequate because it was not universally reproducible, so they considered a few alternate definitions, and, in 2019, redefined it to the current definition. [https://www.youtube.com/watch?v=ZMByI4s-D-Y This video from 2013], also by Veritasium, explains the shortcomings of Le Grand K and describes a proposed alternate definition that was being considered at that time (although it did not end up being the chosen definition).		In 1973, the SI unit for mass was called the grave. It was defined as being the mass of 1 liter of pure water at its freezing temperature. The grave was renamed to the kilogram, and later, in 1889, it was redefined as the mass of a specific sample of a platinum alloy. The sample is called "Le Grand K" and is kept in a humidity-controlled vault just outside of Paris, France. This definition was inadequate because it was not universally reproducible, so they considered a few alternate definitions, and, in 2019, redefined it to the current definition. [https://www.youtube.com/watch?v=ZMByI4s-D-Y This video from 2013], also by Veritasium, explains the shortcomings of Le Grand K and describes a proposed alternate definition that was being considered at that time (although it did not end up being the chosen definition).