How are lower pairs characterized in terms of surface contact___________________?
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Answer: B. surface contact between the two elements when in motion
Explanation
Lower pairs require mating elements to maintain broad surface contact during relative movement. This large contact area helps distribute mechanical loads effectively across the working surfaces. Surface contact distinguishes lower pairs from higher pairs which rely on point or line contact. Kinematic pairs categorize how machine components connect and move relative to each other. Examples of lower pairs include sliding pairs, turning pairs, and helical screw pairs. Lower pair designs are robust and commonly found in heavy machinery and structural mechanisms.
Hydraulic cylinders and slider cranks utilize lower pairs to handle high operational forces. Surface contact minimizes local pressure concentrations, reducing wear in high-load machine joints. Engineers select lower pairs when durability and load-bearing capacity are primary design priorities. Option A describes higher pairs featuring point or line contact instead of surface contact. Option C refers to unconstrained or unfastened assemblies rather than proper kinematic pairs. Option D defines general relative motion without specifying the crucial surface contact criterion.
- Subject
- Engineering
- Category
- Mechanical Engineering
- Topic
- —
- Difficulty
- medium
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