motor slip vs rotational speed
Slip is not a special term, it is essential to the development of torque by an induction motor. The induction motor equivalent circuit is developed based on using per-unit slip to show the conversion of electrical energy to mechanical energy. Many calculations would be more complex if rotational speed were to be used. There are situations in which it is more appropriate to use speed in radians per second or revolutions per minute. As you work through various derivations and calculations, it should be apparent which is most appropriate. Note that some formulae use both slip and speed. That may seem awkward, but if you look closely at the formula, you will see that using per-unit slip simplifies the formula.