Finding name of a process?

When the program goes unresponsive, open Activity Monitor and see if a process is followed by a message in red which says unresponsive. You can get the name of the process from there.

Use the pkill command.

From the man page (man pkill)

The pkill command searches the process table on the running system and signals all processes that match the criteria given on the command line.

Before issuing the pkill command, it's useful to test it out by using the pgrep command first (from man page: "find or signal processes by name").

Once you are certain that pgrep is finding the processes you are interested in killing, issue the pkill command.