Select the hot single answer for each question below. Each correct answer is wor
ID: 1710971 • Letter: S
Question
Select the hot single answer for each question below. Each correct answer is worth 2 points. 1. Internal bending moments (M) cause stresses on a cross-section. (A)Normal (B) Shear (C) Normal and shear (D) Deflecting 2. The stresses caused b > Bending Moments. (A)arc uniform over the entire cross section (B)vary linearly along the direction of the cross-section perpendicular to the bending moment vector (C) vary parabolically along the direction of the cross-section perpendicular to the bending moment sector (D) None of the above 3. Considered alone, a bending moment always creates a combination of _on the cross-section. (A) compression and tension (B) positive and negative shear (C) moments of inertia (D) differential elements 4. Does increasing the depth of a beam always increase the max min stresses due to bending? Why? (A) Yes. sigma = -MY/l (if "y" gets bigger, then the magnitude of the stress must increase as well). (B) Yes An increase in depth will always result in the same or lower moment of inertia. (C) No. An increase in depth may result in a higher moment of inertia "I", which may counteract the increase in " y" and reduce the stress (D)None of the above 5. A positive bending moment about the z-axis (M_x) causes compression on the of the cross-section. while a positive bending moment about the y-axis (M_y) causes compression on the _____of the cross-sect ion Assume a right-handed coordinate system. (A) Positive y-side. Negative 2-side (B) Positive y-side. Positive z-side (C) Negative y-side: Negative z-side (D) Negative y-side. Positive z-side (E) None of the aboveExplanation / Answer
1) A
Bending moment doesn't induse shear stress. Therefore Options B and C are wrong. There is no such stress called deflection stress. So, option D is also wrong. Bending moment induses compressive and tensile stresses, which are normal stresses. Hence, option A.
2) B
Stresses caused by Bending Moment are not unifrom over cross section. Therefore, Option A is wrong.
Stress varies linearly and maximum at outer fiber and minimum at neutral axis. Hence Option B.
In option C, it was given parabolic variation which is not the actual case.
3)A
It was already discussed in first question. Bending moment always creats a combination of compression and tension on the cross section. Hence option A is correct.
Shear stresses are not indused with Bending moment. Option B is wrong.
Moment of inertia is cross sectional property and not the answer. option C wrong.
Differential elements are out of discussion.
4)C
An increase in depth causes increase in moment of inertia. Hence option B is wrong.
If moment of inertia increases stress will not be increased. so, option A is aloso wrong.
Stress is inversly proportional to the moment of inertia, so option C is correct.
5)C
Positive Bending moment about z- axis causes compression on the negative y side
Positive Bending moment about y- axis causes copression on the negative z side
Hence all other options except C are eliminated.
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