71. Center of gravity of a solid cone lies on the axis at the height
One-fourth of the total height above base
One-third of the total height above base
One-half of the total height above base
Three-eighth of the total height above the base
Correct answer: (A) One-fourth of the total height above base
72. Center of gravity of a thin hollow cone lies on the axis at a height of
One-fourth of the total height above base
One-third of the total height above base
One-half of the total height above base
Three-eighth of the total height above the base
Correct answer: (B) One-third of the total height above base
73. Center of percussion is
The point of C.G.
The point of metacentre
The point of application of the resultant of all the forces tending to cause a body to rotate about a certain axis
Point of suspension
Correct answer: (C) The point of application of the resultant of all the forces tending to cause a body to rotate about a certain axis
74. Coefficient of friction is the
Angle between normal reaction and the resultant of normal reaction and the limiting friction
Ratio of limiting friction and normal reaction
The friction force acting when the body is just about to move
The friction force acting when the body is in motion
Correct answer: (B) Ratio of limiting friction and normal reaction
75. Columns of given length, cross-section and material have different values of buckling loads for different end conditions. The strongest column is one whose
One end is fixed and other end is hinged
Both ends are hinged or pin jointed
One end is fixed and the other end entirely free
Both the ends are fixed
Correct answer: (D) Both the ends are fixed
76. Coulomb friction is the friction between
Bodies having relative motion
Two dry surfaces
Two lubricated surfaces
Solids and liquids
Correct answer: (A) Bodies having relative motion
77. D' Alembert's principle is used for
Reducing the problem of kinetics to equivalent statics problem
Determining stresses in the truss
Stability of floating bodies
Designing safe structures
Correct answer: (A) Reducing the problem of kinetics to equivalent statics problem
78. During a tensile test on a ductile material
Nominal stress at fracture is higher than the ultimate stress
True stress at fracture is higher than the ultimate stress
True stress at fracture is the same as the ultimate stress
None of these
Correct answer: (B) True stress at fracture is higher than the ultimate stress
79. Dynamic friction as compared to static friction is
Same
More
Less
May be less of more depending on nature of surfaces and velocity