APPSC AMVI flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Gruebler's criterion

For a planar mechanism, degrees of freedom = 3(N − 1) − 2J − H, where N is the number of links, J the number of lower pairs and H the number of higher pairs.

Grashof condition

A four-bar linkage has at least one fully rotating link when the sum of the shortest and longest links is less than or equal to the sum of the other two links.

Quick return ratio

Ratio of cutting stroke time to return stroke time, equal to (360° − α)/α, where α is the crank angle traversed during the return stroke of a shaping machine.

Epicyclic gear train

A gear train in which one or more gears rotate about moving axes; solved by tabulating motion with the arm fixed and then adding the arm's rotation.

Coefficient of fluctuation of speed

Ratio (ω1 − ω2)/ω_mean, where ω1 and ω2 are maximum and minimum angular speeds; the flywheel energy change equals I·ω²·C_s.

Primary unbalanced force

In a reciprocating engine, the inertia force varying with crank angle θ, given by m·ω²·r·cos θ; secondary force varies with 2θ and has smaller magnitude.

Damping ratio

Ratio of actual damping to critical damping, ζ = c/(2√(km)); ζ = 1 is critical damping, ζ < 1 is underdamped and ζ > 1 is overdamped.

Screw jack torque

Torque required to raise a load W is T = W·r·tan(α + φ), where r is the mean radius, α the helix angle and tan φ the friction coefficient.

Single plate clutch torque

Torque capacity T = μ·W·n·r_m, with n = 2 friction surfaces and r_m the mean radius; uniform wear gives r_m = (r1 + r2)/2.

Differential speed relation

When the crown wheel is held, the average of the two half-shaft speeds equals the crown wheel speed, allowing outer wheels to turn faster in a curve.

Ackermann steering condition

For correct steering without tyre scrub, cot δ_o − cot δ_i = w/L, where w is the track width and L the wheelbase of the vehicle.

Weight transfer under braking

Load shifted to the front axle equals m·a·h/L, where h is the centre of gravity height and L the wheelbase; this is why front brakes wear faster.

Ride frequency

Natural frequency of the sprung mass, f = (1/2π)√(k/m); passenger cars are usually tuned to about 1.0 to 1.5 Hz for comfort.

Slip angle

Angle between a tyre's direction of travel and its pointing direction; cornering force rises with slip angle up to a peak and then falls.

Torque converter stall

Condition when the turbine is stationary and the impeller turns at full engine speed, producing maximum torque multiplication, typically about 2:1.

Otto cycle efficiency

Thermal efficiency of the ideal constant-volume cycle, η = 1 − 1/r^(γ−1), where r is the compression ratio and γ the specific heat ratio.

Mean effective pressure

A fictitious constant pressure acting over the power stroke that would produce the same work per cycle; used to compare engines of different size.

Stoichiometric air-fuel ratio

The mass ratio of air to fuel for complete combustion; about 14.7:1 for petrol and about 14.5:1 for diesel, with excess air common in diesel engines.

Octane number

A measure of petrol's resistance to knock, referenced to iso-octane (100) and n-heptane (0); higher octane permits higher compression ratios.

Cetane number

A measure of diesel fuel's ignition quality, based on ignition delay; a higher cetane number means easier cold starting and smoother combustion.

EGR

Exhaust gas recirculation: a portion of exhaust is routed back to the intake, lowering peak combustion temperature and thereby reducing oxides of nitrogen.

Lambda sensor

An oxygen sensor in the exhaust that signals rich or lean mixture to the ECU, enabling closed-loop fuel trimming to maintain stoichiometric operation.

Section 39, Motor Vehicles Act

Requires that no motor vehicle be driven in a public place unless it is registered under the Act and carries a valid certificate of registration.

Section 185, Motor Vehicles Act

Punishes driving under the influence of alcohol, with the statutory limit set at 30 mg of alcohol per 100 mL of blood.

Third-party insurance

Mandatory cover under Section 146 of the Motor Vehicles Act, indemnifying the insured against liability for death, injury or property damage caused to others.

Motor Accident Claims Tribunal

A tribunal constituted under Section 165 of the Motor Vehicles Act to adjudicate compensation claims arising from motor vehicle accidents.

National permit

A permit issued under Section 88 of the Motor Vehicles Act allowing a goods vehicle to operate across state boundaries on payment of the prescribed fee.

Stopping sight distance

The distance needed to stop a vehicle, equal to the lag distance 0.278·V·t plus the braking distance V²/(254·f), with V in km/h.

Space mean speed

The harmonic mean of spot speeds of vehicles passing a section; it reflects travel time over a road stretch and is used in flow-density relations.

Skid speed formula

The speed at which a vehicle was travelling before braking is v = √(2·μ·g·d), where μ is the friction coefficient and d the skid length.

Webster optimum cycle

The delay-minimising signal cycle C_o = (1.5L + 5)/(1 − Y), where L is total lost time and Y the sum of critical flow ratios.

Black spot

A road stretch or junction with an abnormally high frequency or severity of accidents, identified from crash records for targeted safety improvement.