# Appendix C

# Some Physical Constants

## C.1. Mechanical and thermodynamic constants

Speed of light in a vacuum (exact value) |
*c* = 299,792,458 × 10^{8} m/s |

Gravitational constant |
*G* = 6.67259 (85) × 10^{−11} N.m^{2}/kg^{2} |

Standard acceleration of free fall |
*g* = 9.80665 m/s^{2} |

Sideral year |
365.2564 days |

Normal pressure |
*p*_{o} = 1 At = l.01325 × 10^{5} N/m^{2} |

Normal temperature |
*T*_{o} = 273.16 K |

Mechanical equivalent of the calorie |
J = 4.1855 (4) J/Cal |

Mass density of dry air (STP) |
ρ_{o} = 1.2929 kg/m^{3} |

Speed of sound in air (STP) |
*v*_{s} = 331.36 m/s |

Molar volume of ideal gases (STP) |
*V*_{m} = 2.241383 (70) × 10^{−2} m^{3}/mole |

Avogadro number |
*N*_{o} = 6.0221367 (36) × 10^{23} mole^{−1} |

Boltzmann constant |
*K* = 1.380658 (12) × 10^{−23} J/K |

Gas constant |
*R* = 8.314510 (70) J/K.mole |

Acoustic impedance of air (STP) |
*Z*_{a} = 428 N.s/m^{3} |

Threshold of hearing sound intensity |
10^{−2} W/m^{2} |

Stefan-Boltzmann constant |
σ = 5.67051 (7) × 10^{−8} J/m^{2}.s.K^{4} |

Mass density of mercury |
13,595.5 kg/m^{3} |

**Table C.1.** *Mechanical and thermodynamic quantities. Standard g means at sea level and at latitude of 45°. STP means standard temperature (0 °C) and pressure (760 mm Hg)*

## C.2. Electromagnetic and atomic constants

Elementary charge |
*e* = 1.60217733 (49) × 10^{−19} C |

Electron-volt |
eV = 1.6021892 (46) × 10^{−19} J |

Planck constant |
*h* = 6.626075 (40) × 10^{−34} J.s = 4.135669 (11) 10^{−15} eV.s |

Reduced Plank constant |
*ħ* = *h*/2π = 1.054572 66 (63) × 10^{−34 ...} |