<?php   /* Molecule Building Forces © Charles Chandler http://qdl.scs-inc.us/?top=17079 */   define('e_c', 1.60217657 * pow(10, -19)); // elementary charge, in coulombs define('e_kg', 9.10938291 * pow(10, -31)); // mass of electron, in kilograms define('p_kg', 1.67262178 * pow(10, -27)); // mass of proton, in kilograms   function Electricity_n($c1_e, $c2_e, $dist_m) { // Given two quantities of elementary charges, and the distance between // them (in meters), this returns the electric force (in Newtons). $c1 = $c1_e * e_c; // convert elementary charges to coulombs $c2 = $c2_e * e_c; // convert elementary charges to coulombs return (8.9875517873681764 * pow(10, 9) * $c1 * $c2) / ($dist_m * $dist_m); }   function Gravity_n($m1_kg, $m2_kg, $dist_m) { // Given two masses (in kilograms), and the distance between them // (in meters), this returns the gravitational force (in Newtons). return (6.67408 * pow(10, -11) * $m1_kg * $m2_kg) / ($dist_m * $dist_m); }   // By convention, positive force is repulsive, and negative is attractive. $v['+ion to near electron' ] = -Electricity_n(1, 1, 279 / 1e12); $v['+ion to helium nucleus'] = Electricity_n(1, 2, 310 / 1e12); $v['+ion to far electron' ] = -Electricity_n(1, 1, 341 / 1e12);   $v['net electrostatic attraction'] = // -1.4647704356535E-10 $v['+ion to near electron' ] + // -2.9638331557537E-9 $v['+ion to helium nucleus' ] + // 4.8014097123211E-9 $v['+ion to far electron' ]; // -1.9840536001327E-9   $v['+ion to near electron (gravity)' ] = Gravity_n(p_kg, e_kg, 279 / 1e12); $v['+ion to helium nucleus (gravity)'] = Gravity_n(p_kg, p_kg * 4, 310 / 1e12); $v['+ion to far electron (gravity)' ] = Gravity_n(p_kg, e_kg, 341 / 1e12);   $v['net gravitational attraction' ] = // 7.7740147419448E-45 $v['+ion to near electron (gravity)' ] + // 1.3063805538415E-48 $v['+ion to helium nucleus (gravity)'] + // 7.7718338421773E-45 $v['+ion to far electron (gravity)' ]; // 8.745192137286E-49   ?>