### Strength of Materials

11. A cast iron T section beam is subjected to pure bending. For maximum compressive stress to be three times the maximum tensile stress, centre of gravity of the section from flange side is

1. h/4
2. h/3
3. h/2
4. 2/3 h

Correct answer: (A)
h/4

12. A closely coiled helical spring of radius R, contains n turns and is subjected to an axial load W. If the radius of the coil wire is r and modulus of rigidity of the coil material is C, the deflection of the coil is

1. WR3n/Cr4
2. 2WR3n/Cr4
3. 3WR3n/Cr4
4. 4WR3n/Cr4

Correct answer: (D)
4WR3n/Cr4

13. A closely coiled helical spring of radius R, contains n turns and is subjected to an axial loadW. If the radius of the coil wire is r and modulus of rigidity of the coil material is C, the stress developed in the helical spring is

1. WR/πr 3
2. 2WR/πr 3
3. 2WR/πr 2
4. 4WR/πr 2

Correct answer: (B)
2WR/πr 3

14. A column is said to be of medium size if its slenderness ratio is between

1. 20 and 32
2. 32 and 120
3. 120 and 160
4. 160 and 180

Correct answer: (B)
32 and 120

15. A cylinder is said to be thin if the ratio of its thickness and diameter, is less than

1. 45658
2. 43831
3. 42005
4. 43739

Correct answer: (D)
43739

16. A diagram which shows the variations of the axial load for all sections of the span of a beam, is called

1. Bending moment diagram
2. Shear force diagram
3. Thrust diagram
4. Stress diagram

Correct answer: (C)
Thrust diagram

17. A flywheel on a motor goes from rest to 1000 rpm in 6 sec. The number of revolutions made is nearly equal to

1. 25
2. 50
3. 100
4. 250

Correct answer: (B)
50

18. A force acting on a body may

1. Introduce internal stresses
2. Balance the other forces acting on it
3. Retard its motion
4. All of the above

Correct answer: (D)
All of the above

19. A force is completely defined when we specify

1. Magnitude
2. Direction
3. Point of application
4. All of the above

Correct answer: (D)
All of the above

20. A framed structure is perfect if it contains members equal to

1. 2n3
2. nl
3. 2nl
4. 3n2

Correct answer: (D)
3n2

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