ps ux // Will list all processes with its id(PID)

USER  PID  %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
root  1472  0.0  0.2  95464  4752 ?        S<sl 09:31   0:00 /usr/bin/pulsea
root  1475  0.6  1.1  59496 23916 ?        Sl   09:31   0:09 /usr/bin/compiz
root  1477  0.0  0.9 124628 19316 ?        Sl   09:31   0:00 nautilus
root  1483  0.0  0.5 118556 11280 ?        Sl   09:31   0:00 nm-applet --sm-
root  1485  0.0  0.3  27408  7240 ?        Sl   09:31   0:00 bluetooth-apple
root  1500  0.0  0.1  21704  3308 ?        Sl   09:31   0:00 /usr/lib/pulsea
root  1504  0.0  0.4  48420  8352 ?        Sl   09:31   0:00 /usr/lib/evolut
root  1537  0.0  0.1   8644  3148 ?        S    09:31   0:00 /usr/lib/gvfs/g
root  1541  0.0  0.0   1896   508 ?        Ss   09:31   0:00 /bin/sh -c /usr
root  1542  0.0  0.4  28584  9892 ?        Sl   09:31   0:00 /usr/bin/gtk-wi
root  1546  0.0  0.1   7796  2816 ?        S    09:31   0:00 /usr/lib/gvfs/g
root  1548  0.0  0.1  17996  2248 ?        Sl   09:31   0:00 /usr/lib/gvfs/g
root  1551  0.0  0.1   8188  2180 ?        S    09:31   0:00 /usr/lib/gvfs/g
root  1554  0.0  0.1  51544  3564 ?        Ssl  09:31   0:00 /usr/lib/bonobo
root  1563  0.1  0.6  76696 13716 ?        Sl   09:31   0:02 /usr/lib/gnome-
root  1564  0.0  0.5  75424 11224 ?        Sl   09:31   0:00 /usr/lib/gnome-
root  1573  0.0  0.4  54444  8520 ?        Sl   09:31   0:00 /usr/lib/evolut
root  1579  0.0  0.9  33484 18656 ?        S    09:31   0:00 /usr/bin/python
root  1586  0.0  0.6  84924 13324 ?        Sl   09:31   0:00 /usr/lib/indica
root  1589  0.0  0.6  85464 12864 ?        Sl   09:31   0:00 /usr/lib/indica
root  1591  0.0  0.6  40828 14196 ?        Sl   09:31   0:00 /usr/lib/gnome-
root  1592  0.0  0.4  30992  8792 ?        Sl   09:31   0:00 /usr/lib/gnome-

kill -9 PID

eg : kill -9 1475