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Theory of Machines Mcqs

Q:

Hooke’s universal joint is an example of spatial mechanism. True or false?

A) True B) False
 
Answer & Explanation Answer: B) False

Explanation: Hooke’s universal joint is a joint in a rigid rod which allows the rod to bend in any direction. It is included under spherical mechanisms. Thus, the given statement is false.

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91
Q:

In a mechanical system, if the bodies move in a way such that the trajectories of points in the system lie on concentric sphere, then the mechanism is called

A) spatial mechanism B) flexure mechanism
C) planar mechanism D) spherical mechanism
 
Answer & Explanation Answer: D) spherical mechanism

Explanation: In a spherical mechanism, the locus of every point is a curve contained in a spherical surface. These spherical surfaces are concentric.

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109
Q:

Coplanar motion is the motion transformation of any planar mechanism. True or false?

A) True B) False
 
Answer & Explanation Answer: A) True

Explanation: As all the relative motions of the rigid bodies are in a single plane or in parallel plane, the motion transformation is coplanar. Thus, the statement is true.

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95
Q:

Which of the following are not included under planar mechanisms?

A) Hooke’s universal joint B) Plate cam and follower
C) Plane four bar linkage D) Slide crank mechanism
 
Answer & Explanation Answer: A) Hooke’s universal joint

Explanation: Hooke’s universal joint is an example of spherical mechanism as the relative motion of the particles is three dimensional, whereas the rest are examples of planar mechanisms (the relative motion is two dimensional.)

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124
Q:

If the relative motions of the rigid bodies are in one plane or in parallel planes, then the mechanism is called

A) spherical mechanism B) planar mechanism
C) spatial mechanism D) flexure mechanism
 
Answer & Explanation Answer: B) planar mechanism

Explanation: In a planar mechanism, all particles describe plane curves in space and all the curves lie in a single or parallel planes. The relative motions are constrained to a single plane. Hence, the planar mechanism is a 2 – D mechanism.

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195
Q:

Which is the false statement about the properties of instantaneous centre?

A) at the instantaneous centre of rotation, one rigid link rotates instantaneously relative to another for the configuration of mechanism considered B) the two rigid links have no linear velocities relative to each other at the instantaneous centre
C) the two rigid links which have no linear velocity relative to each other at this centre have the same linear velocity to the third rigid link D) the double centre can be denoted either by O?? or O??, but proper selection should be made
 
Answer & Explanation Answer: D) the double centre can be denoted either by O?? or O??, but proper selection should be made

Explanation: The following properties of the instantaneous centre are important from the subject point of view :
1. A rigid link rotates instantaneously relative to another link at the instantaneous centre for the configuration of the mechanism considered.
2. The two rigid links have no linear velocity relative to each other at the instantaneous centre. At this point (i.e. instantaneous centre), the two rigid links have the same linear velocity relative to the third rigid link. In other words, the velocity of the instantaneous centre relative to any third rigid link will be same whether the instantaneous centre is regarded as a point on the first rigid link or on the second rigid link.

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90
Q:

If there are redundant constraints in the chain and it forms a statically indeterminate structure, what is the degree of freedom or the mobility of this structure?

A) 0 B) 1
C) 2 D) Less than 0
 
Answer & Explanation Answer: D) Less than 0

Explanation: If n ?-1, then there are redundant constraints in the chain and a statically indeterminate structure is formed. The structure is called a preloaded structure as some stress is created within the link so that it has negative mobility.

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