# Aircraft Design Questions and Answers – Structural-Analysis Fundamentals

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This set of Aircraft Design Multiple Choice Questions & Answers (MCQs) focuses on “Structural-Analysis Fundamentals”.

1. When we step on an upright soda can, it would fail due to __________
a) crippling
b) bending
c) torsion
d) shearing

Explanation: When we step on an upright soda can, it would fail due to crippling. Here, walls of cross section will collapse without warning and the ability to carry load will become virtually zero. This can be viewed as the short Column with very thin walls.

2. A rectangular section has b of 2m and h of 5m. Find centroid coordinates.
a) (1, 2.5)
b) (3, 0)
c) (4, 2)
d) (2, 4.8)

Explanation: For rectangle, centroid coordinates = (b/2, h/2)
= (2/2, 5/2) = (1, 2.5).

3. Find the radius of gyration if, moment of inertia I is 160 unit and 10 unit as area.
a) 4 unit
b) 5 unit
c) 2.3 unit
d) 5.6 unit

Explanation: Radius of gyration = $$\sqrt{\frac{Moment \,of\, inertia}{Area}}$$
= $$\sqrt{\frac{160}{10}}$$ = 4 unit.

4. Which of the following is correct?
a) Radius of gyration K = (I/A)0.5
b) Radius of gyration K = (I/A)0.8
c) Radius of gyration K = (I/A)*0.2
d) Radius of gyration K = (I/A)*0.8

Explanation: Above relationship is used to correlate radius of gyration K with moment of inertia I and cross section area A. Correct relationship is given by, radius of gyration K=(I/A)0.5 where, I = moment of inertia and A is the cross section area.

5. The highest compression load which will not cause the elastic column buckling is called _________
b) bernoulli’s theorem
c) newtonian fluid
d) divergence

Explanation: Euler load is defined as the highest compression load which will not cause the elastic column buckling. Euler load is also termed as critical load. Bernoulli’s theorem is used for fluids. Newtonian fluid are those fluids which follow the Newton’s law of viscosity.

6. How do you define slenderness ratio?
a) Ratio of column’s effective length to c/s radius of gyration
b) Ratio of slender body width to the bluff body height
c) Ratio of lift to drag
d) Ratio of Thrust to weight

Explanation: The ratio of column’s effective length to c/s radius of gyration can be termed as slenderness ratio. The effective length of the column is determined based on the end constraints such as pinned joints, fixed ends etc.

7. Column is supported by pin at both the ends and has length of 10 unit. If radius of gyration is 3.16 unit then find slenderness ratio.
a) 3.16
b) 2.13
c) 5.67
d) 0.56

Explanation: Given, column is supported by pin at both the end.
Now, slenderness ratio = effective length/ radius of gyration = 10/3.16 = 3.16.

8. Column has length of 1.2 m and radius of gyration as 1.5m. Determine slenderness ratio. Consider column is fixed at one end free at other end.
a) 1.6
b) 7.8
c) 98
d) 12.45

Explanation: For, given column which is fixed at one end and free at other effective length L = 2*1.2m = 2.4m.
Now, slenderness ratio = effective length / radius of gyration = 2.4/1.5 = 1.6.

9. If a column has slenderness ratio of 2.2 and 1.8 as the radius of gyration. Determine effective length of the column.
a) 3.96
b) 8.98
c) 4.5
d) 1.09

Explanation: Effective length = slenderness ratio*radius of gyration = 2.2*1.8 = 3.96.

10. Determine the actual length of the column which has slenderness ratio of 2.9 and radius of gyration as 1.6. Consider column is fixed at both ends.
a) 9.28
b) 0.0045
c) 2.3674
d) 4.862

Explanation: Given, column is fixed at both ends.
Actual length = slenderness ratio*radius of gyration/0.5 = 2.9*1.6/0.5 = 9.28.

11. A column has effective length as 20unit. Determine Euler load of EI = 1000 unit.
a) 24.67 unit
b) 10 unit
c) 40 unit
d) 50.99 unit

Explanation: Euler load = $$\frac{\pi^2 EI}{(Effective \,length)^2}$$
= $$\frac{\pi^2*1000}{20^2}$$ = 24.67 unit.

12. Stress and pressure are same.
a) True
b) False

Explanation: Stress and pressure are two different properties. Stress is produced due to internal forces. Pressure is result of external force. Stress is defined as internal resistive force per unit cross section area. Unit of pressure and stress will be the same but not their physical explanation.

Sanfoundry Global Education & Learning Series – Aircraft Design. 