Question
Download Solution PDFWhich one of the following is a lower pair?
Answer (Detailed Solution Below)
Detailed Solution
Download Solution PDFExplanation:
Kinematic pair:
A kinematic pair or simply a pair is a joint of two links having relative motion between them.
Kinematics pair can be classified according to:
- Nature of contact
- Nature of relative motion
- Nature of mechanical constraint
Kinematic pairs according to Nature of Contact:
|
Lower pair |
Higher pair |
|
A pair of links having surface or area contact between the members is known as a lower pair. The contact surface of the two links is similar. |
When a pair has a point or line contact between the links, it is known as a higher pair. The contact surface of the two links is dissimilar. |
|
E.g Nut turning on a screw, shaft rotating in a bearing,Tail stock on the lathe bed, all pairs of slider-crank mechanism, ball and socket, piston and cylinder, universal joint etc. |
E.g Wheel rolling on a surface, cam and follower pair, tooth gears, ball and roller bearing, belt drive etc. |
Additional Information
Kinematic pair according to nature of relative motion:
|
Sliding pair |
When two links are so connected that one is constrained to have sliding motion relative to another. Eg. crosshead and guide, rectangular rod in a rectangular hole in a prism. |
|
Turning pair |
When two links are so connected that one is constrained to turn or revolve about a fixed axis of another. Eg. crankshaft turning in a bearing. |
|
Rolling pair |
Two elements of a pair are connected in such a way that one rolls over another fixed link. Eg. Ball and roller bearings, rolling wheel on a flat surface etc. |
|
Screw pair |
If two mating links have a turning as well as sliding motion between them, they form a screw pair. this is achieved by cutting matching threads on the two links. Eg. the lead screw and the nut of a lathe is a screw pair and a bolt with 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. Eg. the ball and socket joint, attachment of a car mirror, pen stand, etc |
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