Ans:
1) Incompletely constrained motion:
When the motion between a pair can take place in more than direction, it is said to be incompletely constrained motion. For example, a circular shaft revolving in a circular hole.
2) Completely constrained motion:
When the motion between a pair can take place in one and only one way , it is said to be completely constrained motion For example, a rectangular shaft revolving in a rectangular hole.
3) Partially (or successfully) constrained motions:
When the constrained motion between a pair is not completed by itself but by some other means, it is said to be partially constrained motion. The motion of shaft in a footstep bearing is successfully a constrained motion when compressive load is applied to the shaft.