Examius
🇮🇳 AFCAT (Air Force Common Admission Test) · flashcards
AFCAT (Air Force Common Admission Test) EKT - Mechanical and Aeronautical Stream Flashcards
60 question-and-answer cards covering EKT - Mechanical and Aeronautical Stream as it is examined in AFCAT (Air Force Common Admission Test). 24 of them are printed below, taken from across the deck — no signup, no paywall on the preview.
24 sample cards from the EKT - Mechanical and Aeronautical Stream deck
Sampled from the end of the deck, so these are different cards from the ones shown on the syllabus page.
Define stress and strain, with their units.
Stress = force per unit area (sigma = F/A), unit Pa or N/m^2. Strain = deformation per unit length (epsilon = change-in-length / original-length), dimensionless.
State Hooke's law and define Young's modulus.
Within the elastic limit, stress is proportional to strain: sigma = E * epsilon. Young's modulus E is the constant of proportionality (stress/strain) in uniaxial loading, with units of Pa.
Define Poisson's ratio.
Poisson's ratio (nu) is the ratio of lateral strain to longitudinal strain under axial loading: nu = -lateral strain / axial strain. For most metals it is about 0.25-0.35.
Give the relations among the elastic constants E, G, K and nu.
E = 2G(1+nu) and E = 3K(1-2nu), where E is Young's modulus, G is shear (rigidity) modulus, K is bulk modulus, and nu is Poisson's ratio. Combined: E = 9KG/(3K+G).
State the simple bending (flexure) equation.
M/I = sigma/y = E/R. Here M is bending moment, I is second moment of area, sigma is bending stress at distance y from the neutral axis, E is Young's modulus, and R is the radius of curvature.
State the torsion equation for a circular shaft.
T/J = tau/r = G*theta/L. T is torque, J is polar moment of inertia, tau is shear stress at radius r, G is shear modulus, theta is angle of twist, and L is shaft length.
Define shear force and bending moment in a beam.
Shear force at a section is the algebraic sum of all transverse forces on one side of it. Bending moment at a section is the algebraic sum of the moments of those forces about that section. Bending moment is maximum where shear force is zero (or changes sign).
What is the polar moment of inertia of a solid circular shaft of diameter d?
J = pi * d^4 / 32. It represents the shaft's resistance to torsional deformation; for a hollow shaft J = pi*(D^4 - d^4)/32.
Define a kinematic pair and a kinematic chain.
A kinematic pair is two links joined so they have constrained relative motion (e.g., revolute, prismatic). A kinematic chain is a series of links connected by pairs such that the relative motion is definite; a mechanism is a chain with one link fixed.
State Grubler's/Kutzbach's degrees-of-freedom criterion for planar mechanisms.
F = 3(n-1) - 2*j1 - j2, where n is the number of links, j1 is the number of lower (one-DOF) pairs, and j2 is the number of higher (two-DOF) pairs. F is the mobility (degrees of freedom).
What is Grashof's law for a four-bar mechanism?
For at least one link to make a full revolution, the sum of the shortest and longest link lengths must be less than or equal to the sum of the other two links (s + l <= p + q).
Define the natural frequency of an undamped single-degree-of-freedom spring-mass system.
omega_n = sqrt(k/m), where k is the spring stiffness and m is the mass. The natural frequency in Hz is f_n = (1/2pi)*sqrt(k/m).
What is resonance and why is it dangerous?
Resonance occurs when the forcing frequency equals the system's natural frequency, causing vibration amplitude to grow very large (limited only by damping). It can cause structural failure and excessive stresses.
Distinguish static balancing from dynamic balancing.
Static balancing eliminates the net unbalanced force (centre of mass on the axis of rotation). Dynamic balancing eliminates both the net unbalanced force AND the net unbalanced couple, so the system is balanced while rotating.
Name the three axes of an aircraft and the rotation about each.
Longitudinal axis: roll (controlled by ailerons). Lateral axis: pitch (controlled by elevators). Vertical (normal) axis: yaw (controlled by the rudder).
Distinguish static stability from dynamic stability of an aircraft.
Static stability is the initial tendency to return to equilibrium after a disturbance. Dynamic stability describes the motion over time, whether the resulting oscillations damp out (positive), persist, or grow (negative).
Define the load factor (n) and stall speed relationship in a turn.
Load factor n = Lift/Weight (expressed in g). In a level turn n = 1/cos(bank angle). Stall speed increases with load factor as V_stall_turn = V_stall * sqrt(n).
What is the function of an aircraft wing spar and rib?
The spar is the main spanwise structural member carrying bending and shear loads (the wing's backbone). Ribs give the wing its airfoil shape and transfer aerodynamic loads from the skin to the spars.
What is a semi-monocoque fuselage structure?
A construction where the skin carries much of the load but is reinforced by internal frames/formers (rings) and longitudinal stringers/longerons. It combines strength with light weight and is the most common aircraft fuselage type.
Name the primary and secondary flight control surfaces of an aircraft.
Primary: ailerons (roll), elevator (pitch), rudder (yaw). Secondary: flaps and slats (increase lift), spoilers (reduce lift/increase drag), trim tabs, and slats/leading-edge devices.
Compare casting, forging, and machining as manufacturing processes.
Casting: molten metal poured into a mould to form a shape. Forging: metal shaped by compressive force (hammering/pressing), giving good grain flow and strength. Machining: material removed by cutting tools to achieve precise dimensions and finish.
What is the difference between hot working and cold working of metals?
Hot working is done above the recrystallization temperature (lower forces, no strain hardening, coarser finish). Cold working is below it (higher strength via strain hardening, better surface finish and tolerance, but higher forces and residual stresses).
What is a factor of safety in machine design?
Factor of safety = ultimate (or yield) strength / allowable (working) stress. It accounts for uncertainties in loading, material, and manufacturing, ensuring the component does not fail under expected service conditions.
Distinguish a clearance fit, interference fit, and transition fit.
Clearance fit: hole is always larger than the shaft (free movement). Interference fit: shaft is always larger than the hole (force/press fit, no movement). Transition fit: tolerances overlap so the result may be slight clearance or slight interference.
What this deck covers
The EKT - Mechanical and Aeronautical Stream deck follows the AFCAT (Air Force Common Admission Test) EKT - Mechanical and Aeronautical Stream syllabus — 4 chapters and 14 topics — so questions land on material that is genuinely examinable rather than trivia around it. That works out to roughly 15.0 cards per chapter.
Answers are written to be recallable, not just readable — averaging about 197 characters, which is long enough to carry the reasoning and short enough to say out loud.
A deck like this earns its keep on the second and third pass. Read the syllabus first so you know the shape of the subject, then use the cards to find the specific facts that have not stuck.
EKT - Mechanical and Aeronautical Stream flashcards FAQ
How many EKT - Mechanical and Aeronautical Stream flashcards are in this AFCAT (Air Force Common Admission Test) deck?
60 cards. This page previews 24 of them, sampled evenly across the deck so you can judge the difficulty before installing anything.
Are these AFCAT (Air Force Common Admission Test) flashcards free?
Yes. The preview here is free to read with no signup, and the full 60-card deck is free inside the Examius app.
What do the EKT - Mechanical and Aeronautical Stream cards cover?
They follow the AFCAT (Air Force Common Admission Test) EKT - Mechanical and Aeronautical Stream syllabus — 4 chapters and 14 topics — so the questions track what is actually examinable.
How should I use these flashcards?
Read the syllabus first so you know the shape of the subject, then drill the deck. Examius schedules each card with spaced repetition, so cards you keep missing come back sooner and ones you know drift further apart.