Solved Question Paper of Recruitment Test (Computer Based Recruitment Test) conducted by UPSC for the Post of Air Safety Officer in the Office of the Directorate General of Civil Aviation held on 11.08.2019.

21.

22.

23. How can thermal contact resistance between two solid bars be reduced?
(A) It can be done by decreasing the joint pressure of compression
(B) It is independent of joint pressure
(C) It can be done by increasing the joint pressure of compression
(D) It can be done by decreasing ambient gas pressure

24. Saturated steam at 100 ℃ is condensing on the shell side of a shell-and-tube heat exchanger. The cooling water enters the tube at 30 ℃ and leaves at 70 ℃. What is the arithmetic mean temperature difference if arrangement is counter flow?
(A) 50 ℃
(B) 40 ℃
(C) 30 ℃
(D) 20 ℃

25. At a point in an airflow the pressure, temperature and velocity are 1 atm, 320 K, and
1000 m/s respectively. What is the total temperature at this point? (Assume the ratio of
specific heats as 1.4 and specific gas constant as 287 J kg-1 K-1)
(A) 671.8 K
(B) 718.8 K
(C) 781.8 K
(D) 817.8 K

26. The relationship between the velocity induced by a vortex tube and the strength (circulation) of the vortex tube can be predicted by
(A) Helmholtz’s law
(B) Prandtl’s law
(C) Biot-Savart’s law
(D) Froude’s law

27. Consider the following statements for the case of steady flow:
1. The magnitude and direction of the velocity vectors at all points are fixed, invariant
with time.
2. Streamlines are different from pathlines.
3. Streamlines and pathlines are identical.

Which of the above statements are correct?
(A) 1 only
(B) 1 and 2
(C) 3 only
(D) 1 and 3

28. A small mass of 0.2 kg is attached to one end of a helical spring and produces an extension of 15mm. The mass is now pulled down 10 mm and set into vertical oscillation of amplitude
10 mm. What is the period of oscillation?
(A) 0.25 s
(B) 0.65 s
(C) 0.85 s
(D) 0.95 s

29.

(A) 162 K
(B) 191 K
(C) 262 K
(D) 291 K