# In the coupling rod mechanism of a locomotive, each of the four pairs is a-

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In the coupling rod mechanism of a locomotive, each of the four pairs is a-
1. Sliding pair
2. Rolling pair
3. Screw pair
4. Turning pair

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Correct Answer - Option 4 : Turning pair

Explanation:

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.

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.

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, coupling rod of a locomotive

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.