Question 61. A wing and tail are geometrically similar, while tail area is one-third of the wing area and distance between two aerodynamic centres is equal to wing semi-span (b/2). In addition, following data is applicable: ∈α = 0.3, CL = 1.0, CLα 0.08/ deg., c = 2.5 , b = 30m , CMac = 0, ηt = 1. The symbols have their usual aerodynamic interpretation. The maximum distance that the centre of gravity can be behind aerodynamic centre without destabilizing the wing-tail combination is

Question 62. A horizontal rectangular plate ABCD is hinged at points A, B and C. AC and BD are diagonals of the plate. Downward force P is applied at D. The upward reactions RA, RB, and RC at points A, B and C, respectively, are

Question 63. A cantilever beam of negligible mass is 0.6 m long. It has a rectangular cross-section of width 8 mm and thickness 6 mm and carries a tip mass of 1.4 kg. If the natural frequency of this system is 10 rad/s, Young's modulus of the material of the beam in GPa is ________

Question 64. Thrust of liquid oxygen - liquid hydrogen rocket engine is 300 kN. The O/F ratio used is 5. If the fuel mass flow rate is 12.5 kg/s, the specific impulse of the rocket motor in Ns/kg is

Question 65. Consider two rockets P and Q fired vertically up with identical specific impulse and a payload of 2 kg. Rocket P has 2 identical stages, and each stage has 200 kg of propellant and 20 kg of structural weight. Rocket Q has a single stage with 400 kg of propellant and 40 kg of structural weight. Neglecting drag and gravity effects, the ratio of the change in velocity of P to that attained by Q is

Question 66. In a 50 % reaction axial compressor stage, the local blade velocity is 300 m/s and the axial component of velocity is 100 m/s. If the absolute inlet flow angle α1 = 45o, the work per unit mass done on the fluid by the stage in kJ/kg is

Question 67. The value of k for which the system of equations x + 2y + kz =1; 2x + ky +8z = 3 has no solution is

Question 68. During the ground roll manoeuvre of an aircraft, the force(s) acting on it parallel to the direction of motion

Question 69. An aircraft in a steady climb suddenly experiences a 10% drop in thrust. After a new equilibrium is reached at the same speed, the new rate of climb is

Question 70. If u(t) is a unit step function, the solution of the differential equation m d2x/dt2 + kx = u(t) in Laplace domain is