title: How to create a gravity effect with Javascript?
body: <p><a href="http://mrdoob.com/projects/chromeexperiments/google_gravity/">Google gravity</a> and <a href="http://code.google.com/p/gravityscript/">gravity script</a> are two nice demonstrations.
  but no source code or tutorials are available. and the original JS files are very big.
  How can I create a Gravity effect with Drag &amp; drop(specially being "<strong>Throw able</strong>" and "<strong>rotatable</strong>" like google gravity) on a certain element?</p>