# Moment of Inertia 22306 MCQ (MOS) FOR CIVIL ENGINEERING MSBTE I- SCHEME 2ND YEAR

This set of Strength of Materials Multiple Choice Questions on “Moment of Inertia”.

1. The axis about which moment of area is taken is known as ____________

a) Axis of area

b) Axis of moment

c) Axis of reference

d) Axis of
rotation

Answer: c

Clarification: The axis of
reference is the axis about which moment of area is taken. Most of the
times it is either the standard x or y axis or the centeroidal axis.

2. Point, where the total volume of the body is assumed to be concentrated
is ____________

a) Center of area

b) Centroid of volume

c) Centroid of
mass

d) All of the mentioned

Answer: b

Clarification: The centroid of the
volume is the point where total volume is assumed to be concentrated. It
is the geometric centre of a body. If the density is uniform throughout
the body, then the center of mass and center of gravity correspond to the
centroid of volume. The definition of the centroid of volume is written in
terms of ratios of integrals over the volume of the body.

3. What is MOI?

a) ml2

b) mal

c) ar2

d) None of the mentioned

Answer: c

Clarification: The formula of the
moment of inertia is, MOI = ar2 where

M = mass, a = area, l =
length, r = distance.

4. What is the formula of radius of gyration?

a) k2 = I/A

b) k2 = I2/A

c) k2 = I2/A2

d) k2 = (I/A)1/2

Answer: a

Clarification: The radius of
gyration of a body about an axis is a distance such that its square
multiplied by the area gives moment of inertia of the area about the given
axis. The formula of radius of gyration is given as k2 = I/A.

5. What is the formula of theorem of perpendicular axis?

a) Izz = Ixx – Iyy

b) Izz = Ixx + Ah2

c) Izz – Ixx = Iyy

d) None of the mentioned

Answer: c

Clarification: Theorem of
perpendicular axis stares that if IXX and IYY be the moment of inertia of a plane section about two mutually
perpendicular axis X-X and Y-Y in the plane of the section then the moment
of inertia of the section IZZ about the axis Z-Z, perpendicular to the plane and passing through
the intersection of X-X and Y-Y is given by the formula

Izz – Ixx = Iyy.

6. What is the formula of theorem of parallel axis?

a) IAD = IG + Ah

b) IAB = Ah2 + IG

c) IAB = IG – Ah2

d) IAB = IG + Ixx

Answer: b

Clarification: The theorem of
parallel axis states that if the moment of inertia of a plane area about
an axis in the plane of area theough the C.G. of the plane area be
represented by IG, then the moment of the inertia of the given plane area
about a parallel axis AB in the plane of area at a distance h from the
C.G. is given by the formula

IAB = Ah2 + IG.

7. What is the unit of radius of gyration?

a) m4

b) m

c) N

d) m2

Answer: b

Clarification: The radius of
gyration = (length4/length2)1/2 = length

So its unit will be
m.

8. What will be the the radius of gyration of a circular plate of diameter
10cm?

a) 1.5cm

b) 2.0cm

c) 2.5cm

d) 3cm

Answer: c

Clarification: The moment of
inertia of a circle, I = πD4/64 = 491.07 cm4

The area of circle = 78.57 cm,

Radius of gyration = (I/A)1/2 = 2.5 cm.

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