How to write Jquery for content Placeholder content?

Question

hii

 

i have button in 

<asp:Content ID="Content1" ContentPlaceHolderID="head" runat="server">
  <asp:Button ID="btnlaunch" runat="server" CssClass="btn_def marr_5 flt_left" Visible="false" OnClick="btnlaunch_Click"/>

 </asp:Content>
i want to disable that button for certain time so i have written jquery :

<script src="http://code.jquery.com/jquery-1.8.3.js"></script>
<script src="http://code.jquery.com/ui/1.10.0/jquery-ui.js"></script>
<script src="//ajax.googleapis.com/ajax/libs/jquery/1.6.1/jquery.js"></script>
<script type="text/javascript">
var enablelanch = function (ele) {
$(ele).removeAttr("disabled");
}
$('[ID$=btnlaunch]').click(function () {
var that = this;
$(this).attr("disabled", true);
setTimeout(function () { enablelanch(that) }, 1000);
});
</script> 

 but its not working so where to write it? in the <asp:content> feild or where?

help me!!