Question

A cam and follower mechanisms constitutes a/an
1. open pair
2. screw pair
3. closed pair
4. spherical pair

Answer 1

Correct Answer - Option 3 : 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 the 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 the door.
• The Slider-crank mechanism does not require much force.

Screw Pair: 

• Two elements of a pair are connected in such a way that one element can turn about the other by screw threads. e.g. the lead screw of a lathe with nut, and bolt with a nut 

Spherical pair: 

• Two elements of a pair are connected in such a way that one element (with the spherical shape) turns or swivels about the other fixed element. e.g. the ball and socket joint, attachment of a car mirror, pen stand, etc.