Maximum possible efficiency of a self-locking screw is

A)
33%
B)
50%
C)
66%
D)
75%

Correct Answer : Option (B) :   50%

Explanation : For self locking screw Ǿ(friction angle)>ἀ (helix angle), hence efficiency < tanǾ/tan(Ǿ+ἀ) or efficiency < tanǾ(1-tan²Ǿ)/2tanǾ.

Recently Updated in Machine Design Questions
Which type of rope drum is preferred?
A)
Drums with helical grooves
B)
Plain cylindrical drums
C)
Both are equally preferred
D)
None of the above

Correct Answer :   Drums with helical grooves

Explanation : They have more bearing surface of the drum and prevent friction between adjacent turns of the rope.

Small sheaves are preferred over large sheaves on what parameters?
A)
Higher cost of small sheaves
B)
Increasingly centrifugal force in large sheaves
C)
Preferring centrifugal force reduction even for more money
D)
None of the above

Correct Answer :   Increasingly centrifugal force in large sheaves

Explanation : Larger sheaves have higher centrifugal forces and higher cost because more material is used in their construction.

The wire rope is subjected to
A)
Tensile Stress
B)
Bending Stress
C)
Both bending and tensile stress
D)
None of the above

Correct Answer :   Both bending and tensile stress

Explanation : There is direct tensile stress due to load being raised as well as bending stress.

Mechanical Engineering MCQ's

Theory of Machines
Engineering Mechanics
Machine Design
Strength of Materials
Engineering Materials
Hydraulic Machines
Thermodynamics
Engineering Drawing
Workshop Technology
Automobile Engineering
Steam Boilers and Engines
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