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. It is a combination of a revolute joint and a sliding joint. This joint has two degrees of freedom.

The combination of force and movement defines power, and a mechanism manages power to achieve a desired set of forces and movement. A mechanism is usually a piece of a larger process, known as a mechanical system or machine.

Most of the machines you encounter in everyday life are complex. However, break them down to their smallest parts and you’re left with simple machines: wheels, levers, wedges and screws. Simple machines magnify, spread out, or change the direction of force, making it easier to move, cut and bind objects.

5. Which of the following is an example of sliding pair? Explanation: When the nature of contact between the element of a pair is such that it can only slide relative to the other, the pair is known as a sliding pair and can be found in piston and cylinder of a reciprocating steam engine. 6.

Belt and pulley3. Belt and pulley3. Cylinder and piston4. Cam and follower Among these, the higher pairs are[IES-2000]a)1 and 4b)2 and 4c)1, 2 and 3d)1, 2 and 4Correct answer is option ‘D’.

If the relative motion between them is completely or successfully constrained, the pair is known as kinematic pair. Explanation: When the two elements of a pair are not held mechanically, they are called open pair. 6. The sliding pairs, turning pairs and screw pairs form lower pairs.

Cam and follower is open pair.

The reason of consideration of belt pulley as lower pair was given that “It is a wrapping element which creates a surface contact therefore it is lower pair.” Therefore Belt and Pulleys are higher pair.

KINEMATIC LINK:  It is defined as the part of machine which has. a relative motion with respect to some other. part of same machine is called Kinematic link or element.

When two links of a kinematic pair are not held together mechanically but remain in contact with each other under the action of the force of gravity or some spring action, then such a pair is called an open pair. EG.

Explanation: When two elements of a pair are connected in such a way that one can only turn or revolve about a fixed axis of another link, the pair is known as turning pair.

16. Crushing Stress (Bearing Stress) • A localized compressive stress at the area of contact between two components having no relative motion between them is known as crushing stress or bearing stress.

Forced closed kinematic pairs – If the contact between the two pairs is maintained by application of force. Door closing mechanism : It forces the door to be closed when opened….

• Cam and roller mechanism.
• Door closing mechanism.
• Slider-crank mechanism.
• Automotive clutch operating mechanism.

Peaucellier mechanism is one of the exact straight line motion mechanism working on lower pair linkages implying eight links rhomboidal system in such a way so as to produce straight line motion at its output.

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