1. Which of the following is a turning pair ?
a) Piston and cylinder of a reciprocating steam engine
b) Shaft with collars at both ends fitted in a circular hole
c) Lead screw of a lathe with nut
d) Ball and socket joint
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.
2. A combination of kinematic pairs, joined in such a way that the relative motion between the links is completely constrained, is called a
a) structure
b) mechanism
c) kinematic chain
d) inversion
Explanation: When the kinematic pairs are coupled in such a way that the last link is joined to the first link to transmit definite motion (i.e. completely or successfully constrained motion), it is called a kinematic chain. In other words, a kinematic chain may be defined as a combination of kinematic pairs, joined in such a way that each link forms a part of two pairs and the relative motion between the links or elements is completely or successfully constrained.
3. The relation between the number of pairs ( p ) forming a kinematic chain and the number of links (l) is
a) l = 2p – 2
b) l = 2p – 3
c) l = 2p – 4
d) l = 2p – 5
Explanation: If each link is assumed to form two pairs with two adjacent links, then the relation between the number of pairs ( p ) forming a kinematic chain and the number of links ( l ) may be expressed in the form of an equation :
l = 2 p – 4
4. In a reciprocating steam engine, which of the following forms a kinematic link?
a) cylinder and piston
b) piston and connecting rod
c) crankshaft and flywheel
d) flywheel and engine frame
Explanation: Each part of a machine which moves relative to some other part, is known as a kinematic link. The piston and cylinder in a steam engine, form a pair and the motion of the piston is limited to a definite direction relative to the cylinder irrespective of the direction of motion of the crank.
5. A link or element need not to be a rigid body, but it must be a resistant body.
a) True
b) False
Explanation: A body is said to be a resistant body if it is capable of transmitting the required forces with negligible deformation. A link or element need not to be a rigid body, but it must be a resistant body.
6. A railway bridge is an example of a machine.
a) True
b) False
Explanation: When a mechanism is required to transmit power or to do some particular type of work, then it becomes a machine. A railway bridge remains static and there is no motion in it. Hence, it is not a machine.
7. The motion between a pair when limited to a definite direction, irrespective of the direction of force applied, is known as
a) completely constrained motion
b) incompletely constrained motion
c) successfully constrained motion
d) none of the mentioned
Explanation: When the motion between a pair is limited to a definite direction irrespective of the direction of force applied, then the motion is said to be a completely constrained motion.
8. The motion between a pair which takes place in ____________ is known as incompletely constrained motion.
a) one direction only
b) more than one direction
c) opposite direction
d) none of the mentioned
Explanation: When the motion between a pair can take place in more than one direction, then the motion is called an incompletely constrained motion.
9. When the connection between the elements forming a pair is such that the constrained motion is not completed by itself, but by some other means, the motion is said to be a completely constrained motion.
a) True
b) False
Explanation: When the motion between a pair is limited to a definite direction irrespective of the direction of force applied, then the motion is said to be a completely constrained motion.
When the connection between the elements forming a pair is such that the constrained motion is not completed by itself, but by some other means, the motion is said to be a successfully constrained motion.
10. The example of completely constrained motion is
a) motion of a piston in the cylinder of a steam engine
b) motion of a square bar in a square hole
c) motion of a shaft with collars at each end in a circular hole
d) all of the mentioned
Explanation: When the motion between a pair is limited to a definite direction irrespective of the direction of force applied, then the motion is said to be a completely constrained motion. In all the above mechanism, motion is limited, so they all are examples of completely constrained motion.