Question 21. Data for an airplane are given as follows: weight W = 30kN, thrust available at sea-level T0 = 4000 N, wing planform area S = 30 m2, maximum lift coefficient CL max = 1.4, and drag coefficient CD = 0.015 + 0.024 C2L. Assume air density at sea-level P∞ = 1.22 kg/ m3. Stall speed of the airplane in m/s is

Question 22. An aircraft is flying at Mach number M = 1.5, where the ambient temperature is 250 K. The stagnation temperature of gases at the entry to the nozzle is 800 K. The
nozzle is choked and always under expanded. Assume the molecular weight of the exhaust gases to be 29, the ratio of specific heats to be 1.4 and the universal gas constant is 8314 J/kmol-K. For which one of the nozzle exit Mach numbers given below is the propulsive efficiency highest?

Question 23. A wing-body alone configuration airplane with a wing loading of W/S = 1000 N/m2 is flying in cruise condition at a speed V = 90m/s at sea-level (air density at sea-level P∞ = 1.22 kg/m3). The zero lift pitching moment coefficient of the airplane is Cwbmac = Cm0 = -0.06 and the location of airplane aerodynamic center from the wing leading edge is Xac = 0.25c. Here c is the chord length. The airplane trim lift coefficient CL trim is

Question 24. An aircraft is flying at Mach number M = 1.5, where the ambient temperature is 250 K. The stagnation temperature of gases at the entry to the nozzle is 800 K. The
nozzle is choked and always under expanded. Assume the molecular weight of the exhaust gases to be 29, the ratio of specific heats to be 1.4 and the universal gas constant is 8314 J/kmol-K. For which one of the nozzle exit Mach numbers given below is the thrust highest?

Question 25. Data for an airplane are given as follows: weight W = 30kN, thrust available at sea-level T0 = 4000 N, wing planform area S = 30 m2, maximum lift coefficient CL max = 1.4, and drag coefficient CD = 0.015 + 0.024 C2L. Assume air density at sea-level P∞ = 1.22 kg/ m3. Minimum and maximum speeds of the airplane in level flight condition at sea-level in m/s are
respectively

Question 26. All professors are researchers Some scientists are professors Which of the given conclusions is logically valid and is inferred from the above arguments:

Question 27. Which one of the following statements is NOT TRUE for a supersonic flow?

Question 28. Consider a thin flat plate airfoil at a small angle x to an oncoming supersonic stream of air. Assuming the flow to be inviscid, Cd / C2l is

Question 29. The critical Mach number for a flat plate of zero thickness, at zero angle of attack, is _________

Question 30. A damped single degree-of-freedom system is vibrating under a harmonic excitation with an amplitude ratio of 2.5 at resonance. The damping ratio of the system is ______________