# Strength of Materials Questions and Answers – Torsion Equation

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

1. Torsional sectional modulus is also known as _________
a) Polar modulus
b) Sectional modulus
c) Torsion modulus
d) Torsional rigidity

Explanation: The ratio of polar moment of inertia to radius of section is called Polar modulus or Torsional section modulus. Its units are mm3 or m3 (in SI).

2. ________ is a measure of the strength of shaft in rotation.
a) Torsional modulus
b) Sectional modulus
c) Polar modulus
d) Torsional rigidity

Explanation: The polar modulus is a measure of the strength of shaft in rotation. As the value of Polar modulus increases torsional strength increases.

3. What are the units of torsional rigidity?
a) Nmm2
b) N/mm
c) N-mm
d) N

Explanation: The product of modulus of rigidity (C) and polar moment of inertia (J) is called torsional rigidity. Torsional rigidity is a torque that produces a twist of one radian in a shaft of unit length.

4. The angle of twist can be written as ________
a) TL/J
b) CJ/TL
c) TL/CJ
d) T/J

Explanation: The angle of Twist = TL/CJ
Where T = Torque in Nm
L = Length of shaft
CJ = Torsional rigidity.

5. The power transmitted by shaft SI system is given by __________
a) 2πNT/60
b) 3πNT/60
c) 2πNT/45
d) NT/60 W

Explanation: In SI system, Power (P) is measured in watts (W) ; P = 2πNT/60
Where T = Average Torque in N.m
N = rpm
= 2πNT/ 45 1 watt = 1 Joule/sec = 1N.m/s.

6. Area of catchment is measured in ___________
a) mm3
b) Km2
c) Km
d) mm

Explanation: Catchment area can be defined as the area which contributes the surplus water present over it to the stream or river. It is an area which is responsible for maintaining flow in natural water bodies. It is expressed in square kilometres.

7. ______ catchment area is a sum of free catchment area and intercepted catchment area.
a) Total
c) Combined
d) Overall

Explanation: Combined catchment area is defined as the total catchment area which contributes the water in to stream or a tank. Combined Catchment area = Free catchment area + intercepted catchment area.

8. ___________ has steep slopes and gives more run off.
a) Intercepted Catchment Area
b) Good Catchment Area
c) Combined Catchment Area
d) Average Catchment Area

Explanation: Good catchment area consists of hills or rocky lands with steep slopes and little vegetation. It gives more run off.

9. How many number of rain gauge stations should be installed an area between 250 to 500 km2.
a) 2
b) 4
c) 3
d) 5

Explanation: 3 number of rain gauge stations should be installed an area between 250 to 500 km2.

Area of Basin(Km2) Number of Rain Gauge Stations
< 125 1
125 – 250 2
250 – 500 3

10. Trend of rainfall can be studied from _______
a) Rainfall graphs
b) Rainfall records
c) Rainfall curves
d) Rainfall cumulatives

Explanation: Rainfall records are useful for calculating run off over a basin. By using rainfall records estimate of design parameters of irrigation structures can be made. The maximum flow due to any storm can be calculated and predicted.

11. Estimation of run off “R” is 0.85P-30.48.
The above formula was coined by _____
a) Lacey
b) Darcy
c) Khosla
d) Ingli

Explanation: Run off can be estimated by
R= 0.85P-30.48
Where R = annual runoff in mm
P = annual rainfall in mm.

12. Monsoon duration factor is denoted by ________
a) P
b) S
c) F
d) T

Explanation: Monsoon duration factor is denoted by F.

Class of Monsoon Monsoon Duration Factor (F)
Very Short 0.5
Standard length 1.0
Very long 1.5

13. Runoff coefficient is denoted by _______
a) P
b) N
c) K
d) H

Explanation: The runoff coefficient can be defined as the ratio of runoff to rainfall. Rainfall and runoff can be interrelated by runoff coefficient.
R = KP
K = R/P [K = is a runoff Coefficient depending on the surface of the catchment area].

14. _________ is a graph showing variations of discharge with time.
a) Rising limb graph
b) Crest graph
c) Hydraulic graph
d) Gauge graph

Explanation: Hydrograph is a graph showing variations of discharge with time at a particular point of the stream. The hydrograph shows the time distribution of total run off at a point of measurement. Maximum flood discharge can also be calculated by using hydrograph.

15. Calculate the torque which a shaft of 300 mm diameter can safely transmit, if the shear stress is 48 N / mm2.
a) 356 kNm
b) 254 kNm
c) 332 kNm
d) 564 kNm

Explanation: Given, the diameter of shaft D = 300 mm
Maximum shear stress fs = 48 N/mm2.
Torque = T = π/16 fs D3
= 254469004.9 Nmm
= 254 kNm.

Sanfoundry Global Education & Learning Series – Strength of Materials.

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