UPSSSC JE Mechanical Paper 2 Mock Test - 3 - Mechanical Engineering MCQ

Petrol has a higher auto-ignition temperature, and it won't burn at the compression ratio of a diesel engine without external help. So, the engine won't run. Whereas when you use diesel in petrol engines, it's dangerous. Diesel burns with more power, and it may damage the engine partly or entirely.

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.

Toothpaste tube can be produced by backward hollow extrusion also known as impact extrusion.

In impact extrusion, a heavy punch is allowed to fall over the material/billet and the material/billet takes the shape of the die. Collapsible tubes are made by this process. This process is limited to soft and ductile materials.

1 Bar = 101325 Pascal

1 Bar = 101.325 Kilo Pascal

The temperature at which a given material is completely recrystallised in an hour is defined as the recrystallisation temperature.

The recrystallisation temperature is low if the degree of deformation is high and if the temperature of deformation is low, and/or if the initial grain size is small. The recrystallisation temperature is also very sensitive to the purity of the material.

K.E = 1/2Iω² = 1/2mk².ω²

I is the mass moment of inertia of the flywheel about its axis of rotation in kg-m² = m.k².

Methods of elimination of Gear tooth Interference:

• Use of a larger pressure angle (having a larger pressure angle results in a smaller base circle. As a result, more of the tooth profiles become involute)

• Under-cutting of the tooth (A portion of teeth below the base circle is cut off. When teeth are produced by this process, the tip of one tooth of gear will not contact the non-involute portion of the tooth of other gear)

• Tooth stubbing (In this process, a portion of the tip of the teeth is removed, thus preventing that portion of the tip of the tooth from contacting the non-involute portion of the other meshing tooth).

• Increasing the number of teeth on the gear can also eliminate the chances of interference.

• Increasing the center distance between the meshing gears slightly eliminates interference.

• Tooth profile modification or profile shifting (Using profile shifted gears (gears with non-standard profile) can also be an option to eliminate interference. In profile shifted meshing gears, the addendum on the pinion is shorter compared with standard gears).

Piezometer: It is used to measure the static pressure of the fluid at any section.

Pitot tube: It is used to calculate the dynamic pressure (total pressure – static pressure) in any section.

Orifice meter – It is used to measure the discharge of fluid across a considered section.

Angle of Friction between any two surfaces in contact is defined as the angle which the resultant of the force of limiting friction Film and normal reaction N makes with the direction of normal reaction N.

tanθ = F_lim/N = μ

The angle of repose or angle of sliding α is defined as the minimum angle of inclination of a plane with the horizontal such that a body placed on the plane just begins to slide down.

f = mg sin α

N = mg cos α

tan α = f/N

tan α = tan θ

α = θ

∴ The angle of friction = Angle of repose

Decay of organic matter or putrefaction, the process whereby heterotrophic organisms, including some bacteria, fungi, saprophytic plants, and lower animals, utilize the remains of once-living tissue as a source of nutrition. The polysaccharides, lipids, nucleic acids, and proteins of dead tissue are broken down into smaller organic molecules, often by enzymes that are secreted into the external environment by the bacteria and fungi that are involved; the breakdown products are then readily absorbed by the heterotrophs and are used both as a source of building blocks for the synthesis of their own polysaccharides, lipids, nucleic acids, and proteins and as a source of chemical energy, obtained either by fermentation (in an anaerobic environment) or respiration (in the presence of oxygen). Often during the process of putrefaction, trace elements and nitrogen are released into the environment in forms suitable for uptake by higher plants; this is the basis for the use of decayed organic matter as fertilizer. The disagreeable odor produced as putrefaction takes place is caused by the formation of certain gases, including ammonia and hydrogen sulfide, and certain volatile amines, including putrescine and cadaverine, two products of the breakdown of protein by microorganisms.

Maximum COP is of Carnot COP:

W = 900/4.5 = 200 J/sec

• Stable equilibrium : GM > 0 (M is above G)
• Neutral equilibrium : GM = 0 (M coinciding with G)
• Unstable equilibrium : GM < 0="" (m="" is="" below="" g)="" />

(a) Equilibrium Position (b)Tilted Position

Condition of stable equilibrium for a floating body in terms of centre of buoyancy and the centre of gravity:

• Stable equilibrium: If its centre of gravity is directly below the centre of buoyancy
• Neutral equilibrium: If its centre of gravity is coincident with the centre of buoyancy
• Unstable equilibrium: If its centre of gravity is directly above the centre of buoyancy

A submerged body is in equilibrium when the centre of gravity is located below the centre of buoyancy. If the body is tilted slightly in any direction, the buoyant force and the weight always produce a restoring couple trying to return the body to its original position.

The exact moment at which the inlet and outlet valve opens and closes with reference to the position of the piston and crank shown diagrammatically is known as the valve timing diagram. It is expressed in terms of degree crank angle.

The energy required to raise a mass of 1 centigrade (K or ºC) is the specific massic heat of the substance, multiplied by its mass and 1 centigrade. In the case of 1 kilogram of water: E = (4180 J/(kg×K)) ×1 kg × 1K = 4180 J. You can also use the specific molar heat with the number of moles.

Work = electrical work

=3×100W

=3×100×10×60J

Work (W)=180kJ

Heat transfer, Q=0 (no heat transfer from/to battery)

Crystal structure of Material

FCC: - Ni, Cu, Ag, Pt, Au, Pb, Al, Austenite or Ƴ-iron

BCC: - V, Mo, Ta, W, Ferrite or α-iron, δ-ferrite or δ-iron

HCP: - Mg, Zn

Cobalt: - HCP < 420°C, FCC > 420°C

Chromium: - HCP < 20°C, BCC > 20°C

Glass: - Amorphous

In a reciprocating piston engine, the connecting rod connects the piston to the crank or crankshaft. Together with the crank, they form a simple mechanism that converts reciprocating motion into rotating motion.

In a reciprocating compressor or pump, connecting rods may also convert rotating motion into reciprocating motion.

- Within the piezometer tube, the locus of elevations to which the water would rise if open to the atmospheric pressure represent the Hydraulic grade line (HGL).

- The difference in elevation of the water surface in the successive conduit represents the friction and other minor losses in the conduits.

- If the conduit has a slope equal to the friction slope, then the HGL would be parallel to the conduit, ignoring minor losses.

- Energy grade line (EGL) = HGL + v2/2g

- The EGL will be represented by a series of pitot tubes (small tubes with their end openings pointed upstream) intercepting the kinetic energy of the flow.

Concept:

The difference between the maximum and minimum speeds during a cycle is called the maximum fluctuation of speed. The ratio of the maximum fluctuation of speed to the mean speed is called the coefficient of fluctuation of speed (Cs).

Calculation:

ω_max – ω_min = ± 2% of ω_mean

⇒ ω_max – ω_min = 4% of ω_mean⇒ ω_max – ω_min = 0.04 ω_mean

⇒

It is the diameter of the pitch circle. The size of the gear is usually specified by the pitch circle diameter. It is also called pitch diameter.

Lancashire boiler is the most commonly used boiler which is stationary and hardly used during transportation. It is used in sugar mills and textile industries not only for power generation but for various processes. It is normally used where a large quantity of steam is needed, and therefore water reserve should be in large quantity.

The Cornish boiler, Cochran boiler, and Simple vertical boiler is less than the Lancashire boiler; consequently, the capacity of steam generation is less.

Newtonian fluids are defined as fluids for which the shear stress is linearly proportional to the shear strain rate. Newtonian fluids are analogous to elastic solids (Hooke’s law: stress proportional to strain). Any common fluids, such as air and other gases, water, kerosene, gasoline, and other oil-based liquids, are Newtonian fluids.

where μ is the shear viscosity of the fluid

Fluids for which the shear stress is not linearly related to the shear strain rate are called non-Newtonian fluids examples include slurries and colloidal suspensions, polymer solutions, blood, paste, and cake batter.