# Strength of Materials Questions and Answers – Mass Moment of Inertia

This set of Strength of Materials Multiple Choice Questions & Answers (MCQs) focuses on “Mass Moment of Inertia”.

1. What is the product of the mass and the square of the distance of the center of gravity of the mass from an axis?
a) Moment of inertia
b) Mass moment of inertia
c) Center of gravity
d) Product of inertia

Explanation: The product of the mass and the square of the distance of the center of gravity of the mass from an axis is known as the mass moment of inertia about that axis.

2. What is the unit of mass moment of inertia?
a) m4
b) m6
c) N
d) m2

Explanation: The mass moment of inertia is the product of moment of inertia and area. So L4 x L2 = L6. so its unit will be m6.

3. What is mass moment of inertia of circular plate?
a) Md2/3
b) Md2/12
c) Mr2/4
d) Mr2/3

Explanation: The mass moment of inertia of circular plate is Mr2/4.

4. What is the mass MOI of a rectangular plate about x-axis passing through the C.G of the plate if the y-axis is parallel to d and perpendicular to b?
a) Mb2/12
b) Md2/12
c) Md2/6
d) Mb2/6

Explanation: As the mass MOI is to be find along the x-axis, it would be Md2/12.

5. What is the mass MOI of right circular cone of radius R and height H about its axis?
a) 4MR2/10
b) MR2/10
c) 3MR2/10
d) MR2/12

Explanation: The mass MOI of right circular cone of radius R and height H about its axis is 3MR2/10.

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6. What is the mass MOI of a hollow circular cylinder if R is the outer diameter and r is the inner diameter?
a) M(R + r)/4
b) M(R – r )/4
c) M(R+ r)/2
d) M(R – r)/2

Explanation: The mass MOI of a hollow circular cylinder is M(R + r)/4 where R is the outer diameter and r is the inner diameter.

7. What is the mass MOI of a rectangular plate about y-axis passing through the C.G of the plate if the y-axis is parallel to d and perpendicular to b?
a) Mb2/12
b) Md2/12
c) Md2/6
d) Mb2/6

Explanation: As the mass MOI is to be find along the y-axis, it would be Mb2/12.

8. The product of inertia at the principal axes is _____________
a) Minimum
b) Unit
c) Zero
d) Maximum

Explanation: The moment of inertia about x-axis and about y-axis, on the axis they are zero. So the product of inertia will be zero in the principal axis.

9. What is the unit of product of inertia?
a) mm4
b) mm2
c) mm
d) mm3

Explanation: The unit of product of inertia is same as that of moment of inertia I.e. mm4.

10. What is the product of inertia of the given following section?

a) 50mm4
b) 625mm4
c) 125mm4
d) 250mm4

Explanation: The product of inertia = area x points of C.G
= ( 10×5) x 5 x 2.5 = 625mm4.

11. What is the product of inertia of a circle of diameter 10mm?
a) 1862mm4
b) 1945mm4
c) 1963mm4
d) 2014mm4

Explanation: The product of inertia = area x C.G
= πx 10×10 / 4 x 5×5 = 1963mm2.

Sanfoundry Global Education & Learning Series – Strength of Materials.

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