Mechanical Engineering - Theory of machines - Discussion

Whatever @Ajay Tyagi said is correct.

Rolling only means one degree of freedom. But higher pair is a two degree of freedom.
Ex: wheel Rolling on a Surface,
The Correct answer is = D.

Option (C) With higher pairs, the two elements are in contact at a point or along a line, as in a ball bearing or disk cam and follower; the relative motions of coincident points are dissimilar. Lower pairs are those for which area contact may be visualized, as in pin connections, crossheads, ball-and socket joints and some others; the relative motion of coincident points of the elements, and hence of their links, are similar, and an exchange of elements from one link to the other does not alter the relative motion of the parts as it would with higher pairs.

Lower pair: A lower pair is an ideal joint that constrains contact between a point, line or plane in the moving body to a corresponding point line or plane in the fixed body. A lower pair is one in which there occurs a surface or area contact between two members, e.g. nut and screw, universal joint used to connect two propeller shafts

I think C is correct.

When pair is contain line and surface contact then pair is said to be higher pair.

I agree @Ajay Tyagi.

Answer D is correct:.

Refer to "Relative" mentioned in the question. In pure rolling relative velocity will be zero.

C is the correct option as higher pair involves point contact.

D is the correct answer.

If we consider a cam follower (higher pair) under high speed, then the motion between them is partly turning and partly Sliding.

D is the correct answer as in the case of gears.

I think the answer is (c).

Because higher pair is where there is line or point contact. If there is partly sliding that means surface contact and where surface contact there will be a lower pair not a higher pair.