Sentence:  In this test a * * f tape was pulled between the blocks with a motor and <WSD>pulley</WSD> at a rate of * * f with a clearance of 0.002 '' on each side of the tape . 
Meaning of the word marked with <WSD> tags:  a simple machine consisting of a wheel with a groove in which a rope can run to change the direction or point of application of a force applied to the rope