are denoted by the following symbols and may be taken to have the values below Elementary charge Speed of light in vacuum Planck constant Permeability of vacuum Permittivity of vacuum Unified atomic mass constant Rest mass of proton Rest mass of electron Boltzmann constant Avogadro constant Gravitational ... Write down the expression for the gravitational field, g, at distance r from a point mass of mass m, carefully defining all the terms in your expression. ...