Audio Systems: cassette recorder, homework question, pinch roller

Question

As the capstan on the recorder turns and unwinds the tape on the feed reel, the
circumference of the tape on the reel will become smaller which would appear to cause
the tape passing the head to  become slower. Does the recorder have a constant speed
motor and is the decrease in linear tape speed across the head accounted for in the
recording as the tape passes the electromagnet in the head OR does the unit have a
variable pseed motor and, if so, how is the speed controlled?  

Answer
Part of me thinks that this is a homework question, but here it goes...

The tape movement is controlled by the pinch roller assembly.  The tape is actually pulled out from the cassette at a constant speed.  The takeup side is run using an idler system that provides enough tension to pull the tape into the cassette.
Dan