# Strength of Materials Questions and Answers – Trusses – 2

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This set of Strength of Materials Multiple Choice Questions & Answers focuses on “Trusses – 2”.

1. The economical spacing of roof trusses works out to be _________ span.
a) 1/2 to 1/5 span
b) 1/3 to 1/5 span
c) 1/2 to 1/3 span
d) 1/4 to 1/6 span

Explanation: The economical spacing of roof trusses works out to be 1/3 to 1/5 of the span. A structure that is composed of a number of line numbers connected at the ends to form a triangulated framework is called a truss.

2. The top chord members of roof truss is called ___________
a) Common rafters
b) Principal rafters
c) Main tie
d) Pitch

Explanation: The top chord members of roof truss are called principal rafters. They support the roof covering through purlins. They are mainly compression members.

3. The bottom chord member of truss is known as ___________
a) Main tie
b) Principal rafters
c) Common rafters
d) Purlins

Explanation: The bottom chord member of the truss is known as the main tie. It is usually in tension and takes compression if reversal of loads occurs due to wind load intensity.
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4. _______ is a roof beam supported by roof truss.
a) Ridge line
b) Eve
c) Principal rafter
d) Purlins

Explanation: Purlin is a roof beam supported by roof truss. The purlin is designed as a beam subjected to bending moment about to axes. The various loads used in design of purlins are:

5. The ratio of rise to span of truss is called a ___________
a) Slope
b) Splay
c) Pitch
d) Tie

Explanation: Pitch of roof truss is defined as the ratio of rise to the span of a truss. It should be 1/6 for G I sheets, 1/12 for AC sheets and ¼ when snow load occurs besides wind load.

6. The angle of repose is zero for ______________
a) Water
b) Masonry
c) Soil
d) Cement

Explanation: Angle of repose is defined as the maximum natural slope at which the soil particles will rest due to internal friction if left unsupported for long time. Angle of repose of soil depends on its nature and moisture content. For water, the angle of repose is zero.

7. Biological Oxygen Demand (BOD) of safe drinking water must be ________
a) 10
b) 15
c) 5
d) 0

Explanation: The water should be free from BOD to ensure it as fit for drinking. According to standards of potable water, free ammonia should not be more than 0.15 ppm and nitrites should not be more than 20 ppm.

8. The most common coagulant is _____________
a) Magnesium sulphate
b) Alum
c) Chlorine
d) Salt

Explanation: The substance which is used for coagulation is known as a coagulant. Alum has proved to be an effective covalent and it is widely used the coagulant is effective between pH range of 6.5 to 8.5.

9. The process of forming thick gelatinous precipitates is known as ___________
a) Sedimentation
b) Flocculation
c) Coagulation
d) Filtration

Explanation: When coagulants are dissolved in water, they produce thick gelatinous precipitates. This precipitate is known as floc and the process is known as flocculation. The floc is heavy and hence it starts to settle down at the bottom of the tank.

10. What is the desirable limit of calcium in drinking water?
a) 45 mg/l
b) 60 mg/l
c) 75 mg/l
d) 90 mg/l

Explanation: According to Indian standards

Parameter Desirable Limit (ppm)
Nitrates 45
Calcium 75
Magnesium < 30

11. Oxidation is done in __________ method.
a) Sedimentation
b) Filtration
c) Coagulation
d) Aeration

Explanation: Aeration is a method by which water is brought in close contact air so as to absorb oxygen for the reduction of taste, odour etc. by virtue of oxidation.

12. Which of the following is a method of aeration?
a) Mechanical straining
c) Biological metabolism
d) Electrolytic changes

Explanation: Usage of the cascade is a method of aeration, in which the water is allowed to fall over a series of concrete steps. During the fall, the water gets thoroughly mixed with the atmospheric air and gets aerated.

13. Which of the following is not a method of chlorination?
a) As bleaching powder
b) As free chlorine gas
c) As chloramines
d) Use of chloramines

Explanation: Use of chloramine is a method of disinfection. It is found that chlorine alone is not stable in water but when it is mixed in water with ammonia, it forms compounds known as chloramines. These are very effective in killing bacteria.

14. Bulk modulus is denoted by __________
a) A
b) E
c) K
d) V

Explanation: The ratio of direct stress to corresponding volumetric strain is found to be constant which is called as bulk modulus
Bulk modulus = Direct stress/Volumetric strain.
• It is denoted by “k”.

15. The stress corresponding to 0.2% of strain in the stress-strain curve is _________
a) Proof stress
b) Working stress
c) Direct stress
d) Tenacity

Explanation: The stress corresponding to 0.2% of strain in the stress-strain curve of mild steel is known as proof stress and this also taken as yield stress. The maximum stress is generally taken as yield stress.

Sanfoundry Global Education & Learning Series – Strength of Materials.

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