Question 1
Marks : +2 | -2
Pass Ratio : 100%
Which of the following is a turning pair ?
Explanation: When the 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. A shaft with collars at both ends fitted into a circular hole, the crankshaft in a journal bearing in an engine, lathe spindle supported in head stock, cycle wheels turning over their axles etc. are the examples of a turning pair.
Question 2
Marks : +2 | -2
Pass Ratio : 100%
When the elements of the pair are kept in contact by the action of external forces, the pair is said to be a
Explanation: When the two elements of a pair are not connected mechanically but are kept in contact by the action of external forces, the pair is said to be a force-closed pair. The cam and follower is an example of force closed pair, as it is kept in contact by the forces exerted by spring and gravity.
Question 3
Marks : +2 | -2
Pass Ratio : 100%
The relation between the number of links (l) and the number of binary joints ( j) for a kinematic chain having constrained motion is given by j = 3/2 I -2 If the left hand side of this equation is greater than right hand side, then the chain is
Explanation: If the left hand side is greater than the right hand side, therefore it is not a kinematic chain and hence no relative motion is possible. Such type of chain is called locked chain and forms a rigid frame or structure which is used in bridges and trusses.
Question 5
Marks : +2 | -2
Pass Ratio : 100%
In a four bar chain or quadric cycle chain
Explanation: A very important consideration in designing a mechanism is to ensure that the input crank makes a complete revolution relative to the other links. The mechanism in which no link makes a complete revolution will not be useful. In a four bar chain, one of the links, in particular the shortest link, will make a complete revolution relative to the other three links, if it satisfies the Grashof ’s law. Such a link is known as crank or driver.
Question 9
Marks : +2 | -2
Pass Ratio : 100%
The motion of a piston in the cylinder of a steam engine is an example of
Explanation: The piston and cylinder in a steam engine form a pair and the motion of the piston is limited to a definite direction (i.e. it will only reciprocate) relative to the cylinder irrespective of the direction of motion of the crank.