_______ is an example of force closed pair.

Explanation:

Self-closed pair:

• When the two elements of a pair are connected together mechanically. The contact between the two can be broken only by destruction of at least one of the members.
• All lower pairs and some higher pairs are closed pairs. Sliding pairs, turning pairs, spherical pairs and screw pairs are also closed pairs.

Forced-closed pair:

• When two links of a pair are in contact either due to force of gravity or some spring action. In this, the links are not held together mechanically e.g. cam and follower pair (because spring is used to keep the motion constrained).
• The door closing mechanism has a torsion spring-loaded follower in contact with door.
• Slider-crank mechanism does not require such force.