function calculate() {
	var l, t, lu, g;
    l = document.getElementById("l").value;
    lu = document.getElementById("lengthUnits").value;
    if(lu == 1){
        g = 9.81;
    }
    else {
        g = 32.2;
    }
    if(l != ""){
		l = parseFloat(l);
		t = (2 * 3.14 * (Math.sqrt(l/g)));
		document.getElementById("T").innerHTML = "T: " + Math.round(t*100)/100 + " s";
	}
}