# Strength of Materials Questions and Answers – Thin Cylinders

This set of Strength of Materials Multiple Choice Questions & Answers (MCQs) focuses on “Thin Cylinders”.

1. If the thickness of plate is negligible when compared to the diameter of the cylindrical, then it is called __________
a) Thick cylinder
b) Thin cylinder
c) Hoop cylinder
d) Circumferential cylinder

Explanation: The thickness of plate is negligible when compared to the diameter of the cylindrical shell, and then it can be termed as a thin cylinder. The radius stress in the cylinder walls is negligible.

2. In thin cylinders, the thickness should be ____________ times of internal diameter.
a) 1/20
b) 1/15
c) 1/30
d) 1/40

Explanation: In thin shells, the stress distribution over the thickness of the material is assumed to be uniform and the wall thickness is equal to or less than 1/ 20 of the internal diameter.

3. Oil tanks, steam boilers, gas pipes are examples of _____________
a) Thick shells
b) Thin cylinders
c) Hoop cylinders
d) Longitudinal cylinders

Explanation: In thin cylindrical shells, the stresses are uniformly distributed throughout the wall. The type of stresses developed in thin cylinders is hoop stress and longitudinal stress. Ex: water supply mains, oil tanks, steam boilers and gas pipes.

4. In _________ shells, the stress distribution is not uniform over the thickness of the material.
a) Thick
b) Thin
c) Hoop
d) Circumferential

Explanation: A cylinder in which the wall thickness is greater than 1 / 20 of internal diameter it is called the thick cylinder.
t>d/20. In thick shells, the stress distribution is not uniform over the thickness of the material.

5. Hydraulic radius is denoted by _________
a) T
b) A
c) R
d) N

Explanation: Hydraulic radius is the ratio of wetted area to the wetted perimeter. It is also known as hydraulic mean depth. It is denoted by “R”.
R = A/P.
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6. Hydraulic depth is a ratio of wetted area to _____
a) Bottom width
b) Top width
c) Diameter

Explanation: Hydraulic depth is the ratio of wetted area to the top with (T). It is denoted by D
D = A/T.

7. What is the hydraulic depth (D) of a rectangular section?
a) y
b) 1/3 y
c) y2
d) y/5

Explanation: The hydraulic depth (D) of a rectangular section is y.

Section Hydraulic depth (D)
Rectangle y
Trapezoid (B+Zy)y / B+2zy
Triangle 12 y

8. In manning’s formula, V = 1/n×m2/3×i1/2. N stands for ___________
a) Coefficient of viscosity
b) Coefficient of rugosity
c) Coefficient of runoff
d) Coefficient of friction

Explanation: In 1889, manning presented a formula according to which the mean velocity of uniform flow in a channel is V = 1/n × m 2/3 × i1/2.
Where n = coefficient of rugosity.

9. What is the coefficient of rugosity for brick lined surface?
a) 0.011
b) 0.012
c) 0.015
d) 0.013

Explanation: The coefficient of rugosity for brick lined surface is 0.015.

Channel Surface Coefficient of Rugosity (n)
Asbestos cement 0.011
Brick 0.015
Cast Iron 0.012
Galvanised Iron 0.016

10. Most economical section is also called as __________
a) Most active section
b) Most effective section
c) Most efficient section
d) Superior section

Explanation: A channel is said to be the most economical if it gives the maximum discharge under given cross-sectional area, bottom slope and roughness. The most economical section is also known as the most efficient section.

11. For most economical section __________ should be minimum.
a) P
b)A
c) R
d)N

Explanation: A channel discharges larger if the hydraulic radius is maximum. The hydraulic radius will be maximum when the wetted perimeter is minimum for a given area. Hence, for most economical section the wetted perimeter should be minimum.

12. A rectangular channel has cross sectional area of 50 m2. If the channel section is to be most economical calculate the depth. Take B = 10m.
a) 10 m
b) 5 m
c) 8 m
d) 12 m

Explanation: Let y be the depth of flow of the channel. For most economical section y = B/2.
Cross-section area of flow A = By
y= 50/10
y= 5 m.

13. _________ are used to change the water level in a canal.
a) Sluice gates
b) Lock gates
c) Check gates
d) Scour gates

Explanation: Gates which are used to change the water level in a canal or a river are known as lock gates. If a canal or a river has a vertical fall at any section, it is necessary to raise or lower the water level in order to transfer the boat from upper water level to lower one.

14. The flow of water is controlled in hydraulic structures by ____________
a) Sluice gates
b) Check gates
c) Lock gates
d) Drain gates

Explanation: In hydraulic structures, the openings are provided to carry water from its storage place to place of utilisation. The flow of water through such openings is controlled by means of sluice gates.

15. The units of discharge are _____________
a) m/s
b) m2/s
c) m3/s
d) m

Explanation: The volume of liquid flowing through any section or channel per unit time is called discharge or rate of flow. It is expressed in m3/s.
It is denoted by “Q”.
1 cumec = 1000 litres/sec.

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