Within the taxonomy of kinematic pairs, do sliding (prismatic) pairs, turning (revolute) pairs, and screw (helical) pairs all belong to the class of lower pairs characterized by surface contact?

Introduction / Context:

Kinematic pairs are divided into lower and higher categories based on contact type. Lower pairs have surface contact, while higher pairs have line/point contact. This question checks whether three common joints—sliding, turning, and screw—are correctly grouped as lower pairs.

Given Data / Assumptions:

• Standard planar/3D mechanism definitions.
• Ideal joints with rigid elements.
• Focus on contact geometry, not on friction model or lubrication.

Concept / Approach:

Sliding (prismatic) pairs maintain surface contact between a slider and guide; turning (revolute) pairs maintain surface contact between pin and bearing; screw (helical) pairs maintain mating surface contact along helical threads. Thus, all three are lower pairs. Higher pairs include cam–follower and gear tooth idealizations (line/point contact).

Step-by-Step Solution:

Verification / Alternative check:

Textbook classifications consistently list these three as lower pairs; only pairs like cams, gears, and pure rolling contacts are higher pairs.

Why Other Options Are Wrong:

• False and the two mixed options: contradict accepted definitions.
• Depends on lubrication: lubrication affects friction/wear, not the geometric contact classification.

Common Pitfalls:

• Confusing ‘‘higher’’ with ‘‘more sophisticated’’—it strictly refers to contact geometry.

Final Answer:

True