Question #6066

important significant numbers used in the world such as speed of light
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Expert's answer

The speed of sound is the distance travelled during a unit of time by a sound wave propagating through an elastic medium. In dry air

at 20 °C (68 °F), the speed of sound is 343.2 metres per second (1,126 ft/s).

This is 1,236 kilometres per hour (768 mph), or about one kilometer in three

seconds or approximately one mile in five seconds.

The gravitational constant, denoted G, is an empirical physical constant involved in the calculation of the gravitational

attraction between objects with mass. It appears in Newton's law of universal

gravitation, and in Albert Einstein's theory of general relativity. It is also

known as the universal gravitational constant, Newton's constant, and

colloquially as Big G. It should not be confused with "little g" (g), which is

the local gravitational field (equivalent to the free-fall acceleration),

especially that at the Earth's surface.

The Planck constant (denoted h), also called Planck's constant, is a physical constant reflecting the sizes of energy quanta

in quantum mechanics. It is named after Max Planck, one of the founders of

quantum theory, who discovered it in 1900. Classical statistical mechanics

requires the existence of h (but does not define its value).

The Planck constant was first described as the proportionality constant between the energy

(E) of a photon and the frequency of its associated electromagnetic wave (ν).

This relation between the energy and frequency is called the Planck relation or

the Planck–Einstein equation:

Since the frequency ν, wavelength λ, and speed of light c are related by λν = c, the

Planck relation can also be expressed as

The Boltzmann constant (k or kB) is the physical constant relating energy at the individual particle level with temperature,

which must necessarily be observed at the collective or bulk level. It is the

gas constant R divided by the Avogadro constant NA:

J K^−1

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