Full Test 1 - EKT Mechanical


50 Questions MCQ Test IAF AFCAT Mock Test Series and EKT for ( ME, EEE, CSE ) | Full Test 1 - EKT Mechanical


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This mock test of Full Test 1 - EKT Mechanical for Defence helps you for every Defence entrance exam. This contains 50 Multiple Choice Questions for Defence Full Test 1 - EKT Mechanical (mcq) to study with solutions a complete question bank. The solved questions answers in this Full Test 1 - EKT Mechanical quiz give you a good mix of easy questions and tough questions. Defence students definitely take this Full Test 1 - EKT Mechanical exercise for a better result in the exam. You can find other Full Test 1 - EKT Mechanical extra questions, long questions & short questions for Defence on EduRev as well by searching above.
QUESTION: 1

If x = cosθ + jsinθ the value of 

Solution:

We can write xn = cos nθ + jsin nθ
The given equation can be written as 
= cos nθ + j sin nθ + cos nθ − j sin nθ
= 2cos nθ

QUESTION: 2

Laplace transform of 3 t4 is

Solution:


QUESTION: 3

Solution:


A = B ⇒ x− 36 = 0 ⇒ x2 = 36 ⇒ x = ±6

QUESTION: 4

Solution:

The given integral is of the beta function. Hence it can be written as

Here n = 4, therefore the integral becomes

QUESTION: 5

A pair of fair dice is thrown, what is the probability of getting a six on both, given atleast one die gets six?

Solution:

A = {getting a six a atleast 1}= 1-{getting no six}

B = {getting a six on both}

Probability of getting a six on both, given atleast one die gets six i.e. Probability of B given A

Also A∩B = B


= 1/11

QUESTION: 6

Solution:

In the limit, we get the indeterminate form i.e. (∞0).
Rewriting the problem:



This implies that the nth root of n approaches 1 as n approaches infinity.

QUESTION: 7

Which of the following forces have zero value of resultant?

Solution:

Equilibrium is the status of the body when it is subjected to a system of forces. If the resultant force is equal to zero it implies that the net effect of the system of forces is zero this represents the state of equilibrium.

QUESTION: 8

Two bulbs when connected in parallel to a source take 100 W each. The total power consumed when they are connected in series with the same source is 

Solution:

Series Circuits:
I1 = I2 = I
Rt = R1 + R2
V= Vt = V1 + V2

Parallel circuits:
V1 = V= V
Rt = (1/R1) + (1/R2)
It = I1 + I2
Power = VI = I2R = V2/R
Two bulbs when connected in parallel to a source take 100 W each.

When two bulbs are connected in series:
Rt = R1 + R= 2R

QUESTION: 9

What is the unit of conductance

Solution:
  • The degree to which an object conducts electricity is known as conductance
  • It is calculated as the ratio of the current which flows to the potential difference present
  • This is the reciprocal of the resistance and is measured in Siemens or mhos
  • Resistance is measured in ohms
QUESTION: 10

The capacitance between two long parallel conducting wires depends upon

Solution:

The capacitance of parallel conducting wires:

Where R is the radius of the wire and d is the distance between conductors

QUESTION: 11

The speed of electromagnetic waves in free space is _____ m/s.

Solution:

The speed of electromagnetic waves in free space is equal to the velocity of light.

QUESTION: 12

The rivet is made of

Solution:

The material of the rivets must be tough and ductile. They are usually made of steel (low carbon steel or nickel steel), brass, aluminium or copper, but when strength and a fluid tight joint is the main consideration, then the steel rivets are used.

QUESTION: 13

A key that has curved bottom to match the shaft. This key is known as________

Solution:

The sunk keys are provided half in the keyway of the shaft and half in the keyway of the hub or boss of the pulley.

A key attached to one member of a pair and which permits relative axial movement is known as feather key. It is a special type of parallel key which transmits a turning moment and permits axial movement.

flat saddle key is a taper key which fits in a keyway in the hub and is flat on the shaft. It is likely to slip round the shaft under load. Therefore, it is used for comparatively light loads.

hollow saddle key is a taper key which fits in a keyway in the hub and the bottom of the key is shaped to fit the curved surface of the shaft. Since hollow saddle keys hold on by friction, therefore these are suitable for light loads. It is usually used as a temporary fastening in fixing and setting eccentrics, cams etc.

QUESTION: 14

If the load on a ball bearing is reduced to half, the life of the ball bearing will

Solution:

For ball bearing:
LP3 = C
L1P13 = L2P23
L= 8L1

QUESTION: 15

When the frictional force helps the applied force in applying the brake, the brake is

Solution:

When the frictional force helps  the applied force in applying the brake, such type of brakes are said to be self energizing brakes.

When the frictional force is great enough to apply the brake with no external force, then the brake is said to be self-locking brake.
The brake should be self-energizing and not the self-locking.

QUESTION: 16

How can shock absorbing capacity of a bolt be increased

Solution:

If the shank of the bolt is turned down to a diameter equal to even slightly less than the core diameter of the thread, then the shank of the bolt will undergo a higher stress. This means that the shank will absorb a large portion of the energy thus relieving the material at the section near the thread. The bolt in this way becomes stronger and lighter and it increase the shock absorbing capacity of the bolt.

QUESTION: 17

A particle while sliding down a smooth plane of 19.86 √2 m length acquires a velocity of 19.86 m/sec. The inclination of plane is:-

Solution:


v2 = u2 + 2as

7.021 = 9.8 × sin θ
sin θ = 0.716
θ = 45.76°

QUESTION: 18

Which of the following are vector quantities?

Solution:

Vector is a quantity that has both magnitude and direction. In contrast to vectors, ordinary quantities that have a magnitude but not a direction are called scalars. For example, displacement, velocity, and acceleration are vector quantities, while speed (the magnitude of velocity), time, and mass are scalars.

QUESTION: 19

If the moment on a beam is increased three times, then to keep the stress in the beam same, the sectional modulus should be:

Solution:



Or simply we can say that for same stress, M∝Z
If M increased to three times, then Z should increase to three times.

QUESTION: 20

A polar moment of Inertia (I) for hollow shaft with external diameter (D) and internal diameter (d) is given by:

Solution:

Polar moment of inertia of hollow shaft 

QUESTION: 21

A cantilever carries a concentrated load (W) at its free end. It's Shear force diagram will be:

Solution:

RA = w

Vx = RA = w
VA = w, VB = w
Hence, S.F.D. is as shown in figure below

QUESTION: 22

If the Euler load for a column is 1000 kN and crushing load is 1200 kN, then the Rankine load will approximately be:

Solution:

QUESTION: 23

In which one of the following situations the entropy change will be negative.

Solution:

In case of constant volume the entropy change is given as

QUESTION: 24

In a reversible heat engine the temperature limits are 100 k and 400 K. If heat output is 200 kJ and heat input is

Solution:

For a reversible heat engine,


QUESTION: 25

Gibb’s free energy functions is a property comprises.

Solution:

Gibb’s free energy function (G)
G = H – TS
G = f(H, T, S)

QUESTION: 26

Heat transfer takes place according to

Solution:

Heat transfer takes place according to second law of thermodynamics. Second law of thermodynamics states that “heat will flow naturally from one reservoir to another at a lower temperature, but not in opposite direction without assistance”.

QUESTION: 27

What is the ratio of thermal conductivity to electrical conductivity equal to?

Solution:


Note:
The Prandtl number, Pr, is the ratio of the momentum diffusivity (kinematic viscosity) to the thermal diffusivity.

The Reynolds number (Re) is the ratio of inertia forces in the fluid to the viscous forces.

Schmidt and Sherwood numbers are the mass transfer coefficient.
Schmidt number (Sc): Ratio of molecular diffusivity of momentum to molecular diffusivity of mass transfer.

Sherwood number (Sh): Ratio of total mass transfer rate to mass transfer by molecular diffusion

Lewis Number represent the relative magnitudes of heat and mass diffusion in the thermal and concentration boundary layers.

Lorenz Number: Wiedemann–Franz law states that the ratio of the electrical to the thermal conductivity was a constant for several metals, at a given temperature.

QUESTION: 28

An impulse hydraulic turbine:

Solution:

Impulse turbine: At the inlet of the turbine, the energy available is only kinetic energy

Example: Pelton Turbine

Reaction Turbine: At the inlet of the turbine, the water possesses kinetic energy as well as pressure energy

Example: Francis Turbine, Kaplan Turbine

QUESTION: 29

The specific gravity of liquids is usually measured by means of a:

Solution:

A hydrometer or areometer is an instrument that measures the specific gravity (relative density) of liquids-the ratio of the density of the liquid to the density of water.

A hygrometer, also known as a psychrometer, is a device that is used to measure the humidity in the air.

A thermometer is a device that measures temperature or a temperature gradient.

A piezometer is a device used to measure liquid pressure in a system by measuring the height to which a column of the liquid rises against gravity.

QUESTION: 30

The cavitation in a hydraulic machine ________.

Solution:

Cavitation is defined as the phenomenon of formation of vapour bubbles of a flowing liquid in a region where the pressure of the liquid falls below its vapour pressure and the sudden collapsing of these vapour bubbles in a region of higher pressure. When the vapour pressure collapse, very high pressure is created.

Effects of cavitation:

(i) The metallic surfaces are damaged and cavities are formed on the surfaces.

(ii) Due to the sudden collapse of the vapour bubble, considerable noise and vibrations are produced.

(iii) Due to cavitation, the metal of the runner vanes and the draft tube is gradually eaten away, which results in lowering the efficiency of the turbine.

QUESTION: 31

Velocity distribution in a turbulent boundary layer follows:

Solution:

Logarithmic law is best representation of turbulent velocity profile.

QUESTION: 32

In a two-dimensional flow in x-y plane,  then the fluid element will undergo

Solution:

Irrotational flow : If the fluid particle don’t rotate about their mass centre while moving in the direction of motion, the flow is called as irrotational flow. (free vortex).

QUESTION: 33

In an interchangeable assembly, shafts of size 25.000±0.040 mm mate with holes of size 25.000±0.020 mm. The maximum possible clearance in the assembly will be

Solution:

Minimum Clearance = Lower limit of hole – Upper limit of shaft

Maximum Clearance = Upper limit of hole – Lower limit of shaft

Max. C = (25.000 + 0.020) – (25.000 - 0.040) = 0.06 mm = 60 microns

QUESTION: 34

Which one of the following crystal systems is valid for gold?

Solution:

God, Silver, Nickel, Copper and Aluminium – All are having F.C.C (Face Centred Cubic) crystal structure.

QUESTION: 35

Gunmetal, which is used in journal bearings, contains

Solution:

Gun metal – Cu 88%, 10% tin, 2% Zn.

QUESTION: 36

18/8 stainless steel contains

Solution:

18/8 signifies 18% Chromium and 8% nickel. It is also called austenitic stainless steel, non-magnetic in nature, Titanium & niobium added to stabilize the carbon.

QUESTION: 37

The coordination number for FCC crystal structure is

Solution:

QUESTION: 38

Which of the following is not considered a basic parameter for arc welding?

Solution:

For arc welding the main parameters are as follows:

Welding current: Welding current is the most influential parameter because it affects bead shape, controls the rate at which electrode is melted and therefore also controls the deposition rate, heat affected zone, the depth of penetration, and the amount of base metal melted.

Arc voltage: Welding voltage varies with the length of the arc between the electrode and molten weld metal. With the increase in arc length, the arc voltage increases.

Welding speed: Welding speed is the linear rate at which an arc is moved along the weld joint. With any combination of welding voltage and welding current, the effect of changing the welding speed confirms to a general pattern, the weld bead becomes smaller.

Electrode size: Electrode size affects the weld bead shape and the depth of penetration at fixed current.

Electrode work angle: The electrode may be held perpendicular to the work-piece or, tilted forward or backward with respect to the weld pool. As the arc stream tends to align itself along the axis of the electrode, the weld pool shape is different in each case, and so is the shape of the weld bead.

QUESTION: 39

Cemented carbide tools are usually provided with:

Solution:

Positive rake – helps reduce cutting force and thus cutting power requirement.

Negative rake – to increase edge-strength and life of the tool

Zero rake – to simplify design and manufacture of the form tools

Negative back rake angle is preferable for carbide tool. Carbide tools are very brittle in nature, so deformation occurs if we provide positive back rake angle.

Positive back rake angle is used for machining low tensile strength and non-ferrous materials. Negative back rake angles are used for machining high tensile strength material, heavy feed and interrupted cuts.

QUESTION: 40

The normal range of compression ratio for Diesel cycle is

Solution:

The normal range of compression ratio for diesel engine is 16 to 20 whereas for spark ignition engines it is 6 to 10. Due to higher compression ratios used in diesel engines the efficiency of a diesel engine is more than that of the gasoline engine.

QUESTION: 41

In Bull engine, which link is fixed?

Solution:

Pendulum pump or Bull engine is an inversion of single slider mechanism. Here slider is fixed.

QUESTION: 42

In Cam follower, which is not a type of motion

Solution:

The follower, during its travel, may have one of the following motions
1. Uniform velocity
2. Simple harmonic motion
3. Uniform acceleration and retardation
4. Cycloidal motion

QUESTION: 43

Which gear train is used for higher velocity ratios in a small space?

Solution:

Epicyclic gear train is the one in which the axes of some of the gears have motion. The said gear(s) would be revolving about external axis or axes. Whereas in other gear trains, the axes of all the gears do not have motion, only the gears rotate on their axes. Planetary gear trains are often employed to make more compact gear reducer (large speed reduction in a small volume) compared to other gear trains. Multiple kinematic combinations (multiple inputs) are possible with planetary gear trains.

QUESTION: 44

At stall, the wing tip stagnation point

Solution:

Stagnation point is a point in a flow field where the local velocity of the fluid is zero. Hence static pressure is at its maximum value at stagnation points.

A stall, also known as a partial or full separation of the airflow over a wing, happens at a critical angle of attack. Stagnation point is always underneath the wing to provide maximum lift due to the angle of attack.

At stall the angle of attack is high and the stagnation point moves towards the lower surface of the wing.

QUESTION: 45

The application of centrifugal compressor leads to

Solution:

Centrifugal compressors have a large frontal area than that of an axial flow compressor of the same rating. This makes the axial flow compressor more suitable for aircraft work.

QUESTION: 46

Which one of the following is a boiler mounting?

Solution:

The boiler mountings are the part of the boiler and are required for proper functioning. It is essential fitting for the safe working of a boiler.

Some of the important mountings are: Water level Indicator, Pressure Gauge, Safety Valve, Fusible Plug, Feed Check Valve, and Steam Stop Valve

The accessories are mounted on the boiler to increase its efficiency. These units are optional on an efficient boiler.

The following accessories are normally used on a modern boiler: Economizer, Superheater, Air pre-heater, Feed water pump, Steam injector, Chimney

QUESTION: 47

During a refrigeration cycle, heat is rejected by the refrigerant in a:

Solution:

In a compressor, the compression of the suction vapour from the evaporator to the condenser pressure takes place.

In a typical refrigerant condenser, the refrigerant enters the condenser in a superheated state. It is first de-superheated and then condensed by rejecting heat to an external medium. The refrigerant may leave the condenser as a saturated or a sub-cooled liquid, depending upon the temperature of the external medium and design of the condenser.

The evaporator is the component of a refrigerator system in which heat is removed from the air, water or any other body required to be cooled by the evaporating refrigerant.

An expansion device in a refrigeration system normally serves two purposes. One is the thermodynamic function of expanding the liquid refrigerant from the condenser pressure to the evaporator pressure. The other is the control function which may involve the supply of the liquid to the evaporator at the rate at which it is evaporated.

QUESTION: 48

In manufacturing management, the term “Dispatching” is used to describe.

Solution:

Dispatching basically is the physical delivery of orders and instruments to all the persons who are involved in actual production and other supporting activities.

QUESTION: 49

The value engineering technique in which experts of the same rank assemble for product development is called

Solution:

Value engineering technique in which experts of the same rank assemble for product development is called brain storming.

QUESTION: 50

Pareto charts are used to

Solution:

Pareto charts have been used in project management, especially Six Sigma, as a useful tool. The Pareto chart shows vertical bars (in descending order) and a line chart depicting the cumulative totals of categories. Pareto charts are an important tool used in quality management. There are at least four instances when creating a Pareto chart is advisable:

  • To analyze the frequency of defects in a process
  • To look at causes in a process
  • To figure out what the most significant problem in a process is
  • To communicate data with others

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