Mechanical Engineering - Theory of machines - Discussion

In case of surface contact that pairs are higher pairs.

In case of line or point contact that pairs are higher pairs.

All the pairs are lower pairs. There is not line or point contact in any of the given options.

Belt and pulley is a example of wrapping pair.

Turning pair: Lower pair.
Screw pair: Lower pair.
Sliding pair: Lower pair.

Where both turning and sliding takes place is a higher pair.

Pure turning or pure sliding is a lower pair.

Kinematic pairs can be normally classified under three headings namely, lower pair, higher pair and wrapping pair. In a lower kinematic pair, the two bodies which are connected by this pair has area contact. Suppose, we talk of two bodies, namely 1 and 2, if they are connected by a lower pair, then at this connection, body 1 will have a surface contact with body 2.

Similarly, in a higher pair the contact between the two bodies has only a line contact or a point contact. Whereas in a wrapping pair, one body completely wraps over the other. The typical example is of a belt and a pulley or a chain and a sprocket where the belt completely wraps around the pulley or the chain completely wraps around the sprocket.

Belt and pulley is higher pair.

Basically, Belt and Pulley is a wrapping pair macroscopically. But actually, there is not surface contact between belt and pulley. As there is mesh-like structure on the surface of the belt which in contact with the pulley. So there are multiple point contacts.

That's why belt drive is a higher pair.

Belt and pulley are lower pairs because there is surface contact. All answers are wrong.

Belt and pulley is a wrapping pair when we observe closely there is no surface contact. Three ia point contact at many places so wrapping pair is close to higher pair.