The pair is known as a higher pair, when the relative motion between the elements of a pair is
A. turning only
B. sliding only
C. rolling only
D. partly turning and partly sliding
The Correct Answer and Explanation is :
The correct answer is D. partly turning and partly sliding.
Explanation:
In kinematics and mechanics, pairs are classified based on the type of relative motion they allow between their elements. The classification involves two main categories: lower pairs and higher pairs.
- Lower pairs: In a lower pair, the relative motion between the two elements is constrained to a single degree of freedom, typically in the form of pure sliding or pure turning. Common examples are sliding pairs (like a piston in a cylinder) and turning pairs (like a wheel on an axle).
- Higher pairs: In contrast, higher pairs allow more complex relative motions between their elements. Specifically, they involve a combination of turning and sliding. This type of motion is more complex and is usually observed in systems where both translational and rotational movements occur simultaneously.
One key example of a higher pair is a cam and follower mechanism, where the follower moves in a way that combines turning (rotational motion) and sliding (translational motion). The cam’s surface often causes the follower to move in an oscillating or linear fashion while it simultaneously rotates, making it a higher pair.
Why option D is correct:
In a higher pair, the relative motion between the parts is not purely rotational or purely translational. Instead, it is a combination of both types of motion, meaning the elements involved experience both turning and sliding simultaneously. This complex motion is what distinguishes a higher pair from a lower pair.
Other options:
- A. Turning only: This describes a lower pair, not a higher pair. A turning pair only allows rotation around a fixed axis.
- B. Sliding only: This also describes a lower pair, which only allows translational motion along a fixed path.
- C. Rolling only: Rolling involves a combination of sliding and turning, but it’s not the primary characteristic of higher pairs.