How to Force Applications and Processes to Quit on OS X
 

If you’ve ever been using your Mac and had an application hang (Spinning Beachball of Death anyone?), you know how annoying it is. One stuck app can bring your system to a crawl, but it’s well within your power to do something about it.

http://www.howtogeek.com/209658/how-...-quit-on-os-x/