**BE (2 ^{nd} Semester)**

**Examination -2009**

** Basic Mechanical Engineering**

**UNIT- I**

1. (a) Give difference between Isothermal and hyperbolic process.

Solve : (any two)

(b) For reversible adiabatic process prove that P V^{Y}= C.

(c)A certain gas occupies a space of 0.3m^{3} at a pressure of 2 bar and a temperature of 11°0. It is heated at a constant volume, until the pressure is 7 bar. Determine :

(i)Temperature at the end of process

(ii)Mass of gas

(iii)Change of Internal Energy

(iv) Change Enthalpy during process

Assume :

C_{P} = 1.005 kJ/kg K.

C_{V} = 0.712 kJ/kg K

R = 287 J/kg K

(d)A compressor is required to provide 0.5 MPa and 200°C air for a stationary power plant. The air intake is at 0.1 MPa and 20°C. The outlet velocity is 25 m/s. Evaluate the work per unit mass needed for an adiabatic compressor.

**UNIT-II**

2. (a) What do you mean by Law of Degradation of Energy.

Solve : (any two)

(b) Prove that ʃ(dө/T)< 0

(c) If 20 kJ are added to a carnot cycle at temperature 100°C and 14.64 kJ are rejected at 0°C, determine the location of absolute zero on the centigrade scale.

(d) For an otto standered cycle with fixed intake and maximum temperatures, find the compression ratio that renders the work per cycle, a maximum and shoe’that the cycle efficiency is given by the expression.

n= [1-(T_{int ake}/T_{max})1/2

**UNIT-III**

3. (a) Determine the dryness fraction of steam if 1 kg of water is in suspension with 39 kg of dry steam.

Solve: (any two)

(b) 1 kg of wet steam at 250°C and with enthalpy of 2500 kJ is confined in a rigid vessel. Heat is supplied until the steam becomes saturated.

Determine.

(i) Initial Pressure of steam

(ii) Final Pressure of steam

(iii) Heat supplied

(c) Define the term mountings and “accessories of boiler. Why the mountings are necessary for a boiler”? Name two mountings and three accessories and discuss their functions.

(d) Steam at a pressure of 4 ber and 0.7 is allowed to expand at a constant volume until the pressure rises to 5.5 bar. Find the final condition of steam and the heat absorbed by 1 kg of steam.

**UNIT- IV**

4. (a) Name any three parts of lath and shaper.

Solve: (any two)

(b) What is gas flame? Explain types of gas flames with neat diagrams.

(c) Explain working principle of lath.

(d) What is function of shaper? Show the principle parts of shaper.

**UNIT- V**

5. (a) Differentiate between Toughness and Hardness.

Solve: (any two)

(b) Draw the stress strain diagrams for ductile and brittle materials showing all the salient points. Also discuss in brief.

(c) A steel bar 2 m long and 40 mm in diameter is subjected to an axial pull of 80kN. Find the length of 20 mm diameter bore, which should be centrally carried out, so that the total elongation should increase by 20% under the pull. Take E for bar materials as 200 GPa.

(d)A steel bar 40 mm x 40mm, 3000 mm long is subjected to an axial pull of 128 kN. Taking *E*=2×10^{5} N/mm^{2} and Poisson’s Ratio as 0.3, calculate the alterations in the length and sides of the bar during the extension.