Mock Test: SSC JE (ME)- 1

T₁ = 27 +273 =300 K

V₁ =V

V₂=3V

T₂ =?

use  P₁V₁/T₁  = P₂V₂/T₂

GIVEN P₁ =P₂

SO V₁/T₁ =V₂/T₂

V/300 = 3V/T₂

 T₂ =900K

= 627°C

Law of thermodynamics is the basis for measurement of temperature and setting its scale. In simple word, Zeroth law of thermodynamics says that “When two bodies are separately in thermal equilibrium with the third body, then the two are also in thermal equilibrium with each other.”

As the hot coffee remains hot for a long time so neither heat nor mass is exchanged with the surroundings and hence it is an example of isolated system.

Q_{supplied = 60KJ}

_{du= -30 KJ}

_{from first law of thermo=}

_{dQ = du + dW}

_{60 = -30 + dW}

_{dW = 90 KJ}

The work is the path function so the work transfer between the system and the surrounding depend on the path that followed by tha system.

1 joule (J) = 1.00 newton meters (N-m)

General gas equation

pv=mrt

at absolute zero kelvin temp.
pressure =zero

that means

0×v= mr×0

therefore volume will be zero at absolute zero kelvin temp.

According to Avogadro's law ,the volume of a gram mole of all gases at the pressure of 760 mm of Hg and temperature of 0 degree centigrade is same and is equal to 22.4 litres.

dU + PdV = dH which is enthalpy

No engine working between two given temperatures can be more efficient than a reversible engine working between the same two temperatures and that all the reversible engines working between the same two temperatures have the same efficiency, whatever the working substance may be.

The leaks in a refrigeration system using Freon are detected by Halide torch which on detection produces greenish flame lighting

The hydrogen passes across the surface of the ammonia. It lowers the ammonia vapor pressure enough to allow the liquid ammonia to evaporate. The evaporation of the ammonia extracts heat from the evaporator. This, in turn, extracts heat from the food storage space, lowering the temperature inside the refrigerator.

 Cetane and alpha-methyl naphthalene are the reference fuels taken for cetane rating.

For maximum power, slightly rich mixture is required in order to burn more fuel and get energy.

The air fuel ratio for different operations is given below

Idling – 10

Cruising – 16

Maximum Power – 13

Cold Starting – 3

A spark plug gap is kept from- 0.3-0.7 mm because 0.3-0.7 is perfect gap for making spark in spark plug.

Ignition quality of petrol is expressed by octane number and that of diesel by cetane number.

Economizer is boiler accessory and others are mounting

Boiler Economiser ( Sometimes Called Economizer ) is the Energy improving device that helps to reduce the cost of operation by saving the fuel. In boilers, economizers are generally Heat Exchangers which are designed to exchange heat with the fluid, generally water.

Surging is caused due to unsteady, periodic and reversal of flow through the compressor when the compressor has to operate at less mass flow rate than a predetermined value

Choking is the condition which occurs in the compressor in which it operates at very high mass flow rate and flow through the compressor can't be further increased as mach number at some part of the compressor reach to unity i.e. to sonic velocity and the flow is said to be choked.

Two Cases
1 DOF - when the sun is constant and planet is roatating as well as revolving around sun and arm rotating.
2 DOF - when sun and arm are rotating and planet is rotating as well as revolving around sun.

Completely constrained motion is a type of constrained motion in which relative motion between the links of a kinematic pair occurs in a definite direction by itself, irrespective of the external forces applied.

Correct Answer :- b

Explanation : The Soderberg line is a more conservative failure criterion and there is no need to consider even yielding in this case.

18/8 stainless steel is nominally 18% chromium and 8% nickel, with the remainder being mainly iron; it does however also contain other elements, but at very low levels. It is also known as 302 or 304 grade stainless steel.

MAXIMUM SHEAR STRESS THEORY (GUEST's or TRESCA's THEORY)

According to this theory, the elastic failure occurs when the greatest shear stress reaches a value equal to the shear stress at elastic limit in a simple tension test. This is used for ductile material

surface tension is often expressed as an amount of force exerted in the surface perpendicular to a line of unit length. The unit then is newtons per metre, which is equivalent to joules per square metre.

For flow over a flat plate, transition from laminar to turbulent boundary layer occurs when Reynolds number at x exceeds Re_x,crit ~ 500,000. Transition may occur earlier, but it is dependent especially on the surface roughness.

The efficiency of a centrifugal pump will be maximum when the blades are bent backward.

Gravitational force i.e. weight should be less than the upthrust force for a body to float

Actually the deformation under a conectrated load P at end will give deformation equals to PL/AE.

The deformation due to self weight is is give by PL/2AE. 

For pure shear, radius is equal to shear stress and the centre lies on the point of intersection of axes.

A couple in mechanics refers to two equal forces that act in opposite direction . The resultant force in a couple is zero, but it does have a moment of force(torque).A couple produces rotational motion in the object it is acting.

The static friction is always greater than the dynamic friction and hence the ratio of a bigger number to a smaller number is more than 1

A framed structure is perfect, if the number of members are equal to ( 2 n- 3) , where n is the no. of joints. In this figure, there are 3 joints ,therefore, (2*3-3) = 3 
That means there are three members , so it is a perfect frame.

In eutectoid reaction, the austenite transforms into a phase mixture of ferrite (containing 0.76% C) and cementite. This phase mixture is known as pearlite. The eutectoid reaction occurs at a constant temperature. This is known as eutectoid temperature and is 723^oC

Magnesium is a powerful inoculant in cast iron. When added in concentrations exceeding 0.04%, it produces a spheroidal form of graphite that improves the iron's strength and ductility. Magnesium is an abundant metal with a price roughly comparable to that of aluminum, albeit usually higher

Correct Answer :- c

Explanation : Quenching Media 

Four commonly used quenching media are :

1.Oil - slowest cooling rate

2. Water - moderate cooling rate

3. Brine - the fastest cooling rate

4. Liquid Nitrogen - used in automatic furnaces, can be very fast cooling.

Trimming is a manufacturing process that is used as a finishing operation for forged parts, in order to remove flash. Flash is a characteristic common in most metal forgings. For that reason trimming, while not technically a forging or even a forming operation in general, is discussed in this section. Trimming basically presses a part through a cutting die that runs the periphery of the work. The cutting die are precisely designed to remove the flash from a particular part. Most often it is desirable to perform this operation while the work is still hot for maximum efficiency, therefore it is usually incorporated into the larger production process. For more delicate forgings, flash can be ground or cut off using different methods. For certain metal forgings, this is an extremely quick and easy method for the removal of the extra material.

The neutral flame has a one-to-one ratio of acetylene and oxygen. It obtains additional oxygen from the air and provides complete combustion. It is generally preferred for welding. The neutral flame has a clear, well-defined, or luminous cone indicating that combustion is complete

Correct Answer :- d

Explanation : Wrought iron is an iron alloy with very low carbon content with respect to cast iron. It is soft, ductile, magnetic, and has high elasticity and tensile strength. It can be heated and reheated and worked into various shapes.

Mandrel is used to hold a hollow bar or a bar with a bore wen turning between live centre and dead cente of a lathe. A moving mandrel is also used for tube drawing

On the planer the work is moved against a stationary tool: on the shaper the tool moves across the work, which is stationary. On the planer the tool is fed into the work; on the shaper the work is usually fed across the tool. The drive on the planer table is either by gears or by hydraulic means. 

Surface grinding is used to produce a smooth finish on flat surfaces. It is a widely used abrasive machining process in which a spinning wheel covered in rough particles (grinding wheel) cuts chips of metallic or nonmetallic substance from a workpiece, making a face of it flat or smooth.