okay, stupid question, but...

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i asked this in another thread, but i thought i'd give it a bump:

okay, i have a really really newbie question (bear with me please )i bought a pc and started to use it on my car with 3m perfect it. i realized after buffing for a while that the perfectit wasn't breaking down into a finer and finer solution as i'd expected it to.

i inspected the pc and realized that it doesn't really have a motor to rotate the head (i know it's orbital and not rotary). but i figured it did both. while it's running i can use my hand to stop the rotation of the pad altogether, not the orbit however. is that the way it's supposed to be? my only previous experience (long ago) was with a pneumatic rotary buffer which, obviously, has tons of cutting power. is my pc broken or was i just mistaken in thinking that it had a motorized rotation in addition to the orbit? or does it work simply by vibrating very quickly on the surface?