/* Energy in springs calculator
   Copyright 2005 by Dale Heatherington (coded Oct 19, 2005) */

function spring(dataform,k,x_min,x_max,k_units,x_units)
{
	var xk;
	var kk;

	if(x_units == "in"){ xk = .0254 }; /* convert inches to meters */
	if(x_units == "ft"){ xk = .3048 }; /* feet to meters */
	if(x_units == "mm"){ xk = .001 }; /* millimeters to meters */
	if(x_units == "cm"){ xk = .01 }; /* centimeters to meters */
	if(x_units == "m"){ xk = 1}; 	/* meters to meters */
	
	if(k_units == "lbf-in"){ kk = 175.125 }; /*lbf-in to Newton-meters */
	if(k_units == "N-m"){ kk = 1 }; /* Newton-meters */
	if(k_units == "dyne-cm"){ kk = 0.001 }; /*dyne-cm to Newton-meters */
	
	x_min = xk * x_min;	/* Convert x to meters*/
	x_max = xk * x_max;
	k = kk * k;		/*convert k to Newton-meters */
	
	PE_min = 0.5 * k * (x_min * x_min);	/* compute PE minimum */
	PE_max = 0.5 * k * (x_max * x_max);	/* compute PE maximum */

	
        dataform.PE.value = PE_max - PE_min;  /* output potential energy in Joules */
        
 }