Mechanical Engineering - Theory of machines - Discussion

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

When the two elements of a pair have a line or point contact when relative motion takes place and the motion between the two elements is partly turning and partly sliding, then the pair is known as higher pair. A pair of friction discs, toothed gearing, belt and rope drives, ball and roller bearings and cam and follower are the examples of higher pairs.

When the two element of pair have a line or point contact when relative motion takes place and the motion between two element is partly turning and partly sliding. Called higher pair Ex. - friction disc, toothed gearing, belt and rope drive, ball and roller bearing, cam and follower.

A pair with point or line contact is HIGHER PAIR. Rolling action may take place with either point or line contact.

For example sphere rolling on the floor represents point contact and if one replaces sphere with cylinder then it becomes line contact.

So answer is C.

Answer is undoubtedly D because higher pair said to be when the two bodies are contact wish other when there is partly sliding and rolling occur.

Ex:: ball bearing between two gear teeth in contact then the bodies are undergo slightly sliding and also rotating.

D is right. Because in c option, pure rolling is mentioned. Pure rolling means one degree if freedom. i.e Lower pair and partly rolling nd sliding i.e. two degrees of freedom i.e.higher pair. Point or line contact in hp is a general criterion.

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.

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.

Go through the theory of machine if you have studied. Answer as given is correct. And it is obvious that a higher pair to have partial turning and partial sliding action.

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.