Why Do Units on Plank's Constant Include Mass, Length, and Time?

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SUMMARY

Planck's constant has units of m2 * kg / s, which can be understood through its definition as the ratio of energy to frequency (h = E/ν). This relationship highlights the equivalence between energy, mass, length, and time, which was not fully recognized when the units were originally devised. Understanding these units requires a grasp of classical mechanics and the fundamental relationships between these physical quantities.

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The units on Plank's constant is m^2 * kg / s
I'm new to all of this stuff so... Why?
 
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Because when people devised units, they didn't realize that there are equivalence relationships between length, mass and time.

But to more directly answer your question, Planck's constant really has units of (energy)(time). To see this, note that Planck's constant can be defined by the ratio of the energy and frequency of a photon :

[tex]h= \frac{E}{\nu}.[/tex]

In order to explain the relationship of energy to units of mass, length and time, you might want to consider basic formulae from classical mechanics.
 

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