# Tag Info

21

In physics, the Planck constant may be used as a natural unit. If you want to switch to another unit system, use UnitConvert[]. For example, you can switch to standard SI units this way: UnitConvert[Quantity[1, "PlanckConstant"], "SIBase"] which will give you: Quantity[6.626070*10^-34, ("Kilograms" ("Meters")^2)/("Seconds")] This can be done at the ...

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Rightly or wrongly, if the unit specification is unknown, then WA is used behind the scenes to decide if it could be interpreted as a standard unit. You can see this with the error message provided: Quantity["AccelerationOfGravity"] Quantity::unkunit: Unable to interpret unit specification AccelerationOfGravity. Quantity["AccelerationOfGravity"] So,...

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QuantityMagnitude@UnitConvert[Quantity["GravitationalConstant"]] 6.67*10^-11

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kglr comment is one way to solve your problem, but it can also be solved by making sure you give UnitConvert a machine number in its 1st argument. UnitConvert[Quantity[1., "SpeedOfLight"], "meters/sec"] // EngineeringForm 299.792*10^(6)m/s UnitConvert[Quantity[1., "SpeedOfLight"], "meters/sec"] // ScientificForm 2.99792*10^(8)m/s If you are going to ...

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These days a great place to start is Wolfram|Alpha: But to answer your direct question: UnitConvert@Quantity["MolarGasConstant"] Then convert the output to SI or Metric units: UnitConvert[ Quantity[8.31446, ("Kilograms" ("Meters")^2)/( "Kelvins" "Moles" ("Seconds")^2)], "SI"] UnitConvert[ Quantity[8.31446, ("Kilograms" ("Meters")^2)/( "Kelvins" "Moles" (...

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From the documentation for Unit Discovery, "You can use both WolframAlpha and Quantity to discover different units and physical constants using their various common names and abbreviations." WolframAlpha["Coulomb's Constant"]

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Are you trying to get the numeric value in MKS units? That can be done as follows. g = SemanticInterpretation @ "acceleration of qravity" // UnitConvert Quantity[196133/20000, ("Meters")/("Seconds")^2] To get the numeric value you could do QuantityMagnitude[1. g] or make use of how the Quantity is structured N @ g[] Both give 9.80665 The ...

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As Carl notes, you can express the gas constant in terms of base SI units with r = UnitConvert[Quantity[1, "MolarGasConstant"]] Quantity[8.31446, ("Kilograms"*"Meters"^2)/("Kelvins"*"Moles"*"Seconds"^2)] and then use QuantityMagnitude[] to extract the number, or QuantityUnit[] to extract the unit: {QuantityMagnitude[r], QuantityUnit[r]} {8.31446, ("...

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You should use the Physical Constants Package by using << PhysicalConstants` When you enter now PlanckConstant you directly get the Planck Constant. With PlanckConstant/(Joule Second) you get the Planck Constant without units.

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