SECTION-3

#### Strength of Material MCQ

##### Q51. Choose the wrong statement

(a) To avoid the shear failure of a material (which is subjected to a tensile load) along a plane at an angle of 45° to the direction of tensile stress, the material should have its shear strength at least equal to half the tensile strength.
(b) Key is made weaker link in the design of pulley, key and shaft.
(c) The planes, which carry no shear stress, are known as principal planes.
(d) The normal stress on an oblique plane will be maximum when the angle of oblique plane with cross-section is 45°.

Ans:(d) The normal stress on an oblique plane will be maximum when the angle of oblique plane with cross-section is 45°.

##### Q52. Choose the correct statement

(a) The circumferential stress induced in a thin-walled cylindrical vessel is (pd/4t).
(b) The longitudinal stress induced in a thin walled cylindrical vessel is (pd/2t).
(c) The strain in a cylindrical bar (of length L metres) which deforms by l cm is 0.01 l/L.
(d) When a body is subjected to a direct tensile stress (p), the maximum tangential stress is equal to
the direct tensile stress.

Ans:(c) The strain in a cylindrical bar (of length L metres) which deforms by l cm is 0.01 l/L.

##### Q53. A body is subjected to two principal stresses σ1 and σ2 in two mutually perpendicular directions. Obliquity is the angle made by

(a) oblique plane with the direction of σ1
(b) oblique plane with the direction of σ2
(c) the line of action of the resultant stress with the normal of the oblique plane
(d) the line of action of the resultant stress with the oblique plane.

Ans:(d) the line of action of the resultant stress with the oblique plane.

##### Q54. The obliquity (φ) is expressed mathematically as

(a) tan φ =σ1r
(b) tan φ =σ2r
(c) tan φ =σ1n
(d) tan φ =σrn
where σ1 and σ2 = Two principal stresses at right angles, σr = Resultant stress
σr and σn = Tangential and normal stresses on an oblique plane.

Ans:(b) tan φ =σ2r

##### Q55. Two principal tensile stresses of magnitudes 400 N/cm2 and 200 N/cm2 are acting at a point across two perpendicular planes. An oblique plane makes an angle of 30° with the major principal plane. The normal stress on the oblique plane will be

(a) 600 N/cm2
(b) 350 N/cm2
(b) 86.6 N/cm2
(d) 173.2 N/cm2

Ans:(b) 350 N/cm2

##### Q56. Two principal tensile stresses of magnitudes 400 N/cm2 and 200 N/cm2 are acting at a point across two perpendicular planes. An oblique plane makes an angle of 30° with the major principal plane, the tangential stress along the oblique plane will be

(a) 600 N/cm2
(b) 350 N/cm2
(c) 86.6 N/cm2
(d) 173.2 N/cm2

Ans:(c) 86.6 N/cm2

##### Q57. The obliquity is equal to

(a) tan–1  86.6/350
(b) tan–1 86.6/600
(c) tan–1 350/86.6
(d) tan–1 600/86.6

Ans:(a) tan–1  86.6/350

##### Q58. Choose the wrong statement

(a) The resultant, of the two equal and like principal stresses, on any plane is equal to either of the principal stresses.
(b) The resultant stress of the two equal and like principal stresses on any plane, is normal to the plane.
(c) The resultant, of the two equal and unlike principal stresses, on any plane is equal is to either of the principal stresses.
(d) The resultant stress of two equal and unlike principal stresses on any plane, is normal to the plane.

Ans:(d) The resultant stress of two equal and unlike principal stresses on any plane, is normal to the plane.

##### Q59. Two unequal like principal stresses are acting at a point across two perpendicular directions. An oblique plane makes an angle θ with the major principal plane. As the angle θ increases, obliquity (φ)

(a) decreases
(b) increases
(c) first increases then decreases
(d) remains constant.

Ans:(b) increases

##### Q60. Two unequal like principal stresses are acting at a point across two perpendicular directions. An oblique plane makes an angle θ with the major principal plane. As the angle θ increases, obliquity (φ), the maximum obliquity (φmax) is given by

(a)  φmax = tan–1 σ1 −σ212
(b) φmax = tan–1 σ1 +σ212
(c) φmax = sin–1 σ1 −σ212
(d) φmax = sin–1 σ1 +σ212
where σ1 = Major principal stress and σ2 = Minor principal stress.

Ans:(a)  φmax = tan–1 σ1 −σ212

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##### Read More Sections of Strength of Material

Each section contains maximum 80 Questions. To practice more questions visit other sections.

Strength of Material MCQ – Section-1

Strength of Material MCQ – Section-2

Strength of Material MCQ – Section-3

Strength of Material MCQ – Section-4

Strength of Material MCQ – Section-5

Strength of Material MCQ – Section-6