Quiz: Mechanical Engineering
Exam: UPSSSC JE
Q1. Consider the following statements:
- Availability is generally conserved.
- Availability can either be negative or positive.
- Availability is the maximum theoretical work obtainable.
- Availability can be destroyed in irreversiblities.
Which of these statements are correct?
(a) 3 and 4
(b) 1 and 2
(c) 1 and 3
(d) 2 and 4
Q2. A body of mass 2 kg and kJ/kg K is available at 600 K. If the atmosphere is 300 K and ln 2=0.693, the maximum work obtainable from the body till it comes to equilibrium with the atmosphere is
(a) 150 kJ
(b) 142 kJ
(c) 184.2 kJ
(d) 190.5 kJ
Q3. Which type of valve is generally used in reciprocating refrigerant compressors?
(a) Mushroom valve
(b) Puppet valve
(c) Plate valve
(d) Throttle valve
Q4. The optimum effective temperature for human comfort is
(a) higher in winter than that in summer
(b) lower in winter than that in summer
(c) same in winter and summer
(d) not dependent on season
Q5. Which of the following set of the materials is most commonly used in catalytic converters for CI engines?
(a) Platinum, palladium and rhodium
(b) Palladium, rhodium and ruthenium
(c) Rhodium, ruthenium and platinum
(d) Ruthenium, platinum and palladium
Q6. If a piece of material neither expands nor contracts in volume when subjected to stress, then the Poisson’s ratio must be
Q7. The state of stress at a point is given by MPa and MPa and The centre of Mohr’s circle and its radius will be
(a)(σx=75 MPa,τxy=0) and 75 MPa
(b) (σx=25 MPa,τxy=0) and 125 MPa
(c) (σx=25 MPa,τxy=0) and 150 MPa
(d) (σx=75 MPa,τxy=0) and 125 MPa
Q8. A wall of thickness 0.6 m has a normal area 1.5 m² and is made up of material of thermal conductivity 0.4 W/mk. The temperatures on the two sides are 800°C and 100°C. What is the thermal resistance of the wall?
(a) 1 W/K
(b) 1.8 W/K
(c) 1 K/W
(d) 1.8 K/W
Q9. If the surface tension of water-air interface is 0.073 N/m, the gauge pressure inside a rain drop of 1 mm diameter will be
(a) 0.146 N/m²
(b) 73 N/m²
(c) 146 N/m²
(d) 292 N/m²
Q10. A body starting from rest moves in a straight line with its equation of motion being
where s is displacement in m and t is time in s. Its acceleration after one second is
(a) 6 m/s²
(b) 2 m/s²
(c) 12 m/s²
(d) 3 m/s²
S1. Ans (a)
Sol. The availability is the maximum useful work obtainable from a system as it reaches the dead state. Conversely, availability can be regarded as the minimum work required to bring the closed system from the dead state to given state. The value of availability cannot be negative. As energy is always conserved, availability is not generally conserved but is destroyed by irreversibility.
S2. Ans (c)
Sol. Plate valve is used in the reciprocating refrigerant compressor.
Sol. In winter the optimum effective temperature is 19°C where as in summer this temperature is 22°C.
S5. Ans (a)
Platinum: for hydro-carbon (HC)
Palladium: for Carbon-mono-oxide
Rhodium: for oxide of nitrogen (NOx)
Poisson’s Ratio is ratio of lateral strain to the longitudinal strain. It is denoted by μ. When volume change on loading is zero, value of μ is 0.5.
S8. Ans (c)
S9. Ans (d)