ELE-101 Elements of Mechanical Engineering (B.Tech., 1st and 2nd Semester, 2122) Time : 3 Hours Maximum Marks : 60 NOTE:- Question No. 1 is compulsory. Attempt other five questions taking at least two from Section A and Section B. Assume the suitable value of any missing data. 1 (a) When neithe mass nor energy is allowed to cross the boundary of the clossed system it is known as : (i) Closed system (ii) Opened system (iii) Isolated system (iv) None of these (b) The relationship between COP and EPR is given by.............. (c) The characteristis equation of gas is : (i) pv = const. (ii) pv = mRT (iii) pv = mR m (iv) pv = RT (d) the ploytropic expansion n in the equation in the equation pvn = const. for constant volume process is : (i) 1 (ii) 1.4 (iii) infinity (iv) 0(zero) (e) Zeroth law of thermodynamics defines : (i) Internal energy (ii) Enthalpy (iii) Temperatre (iv) Pressure (f) 1 Newton = 10-9......... (i) Giga (ii) Micro (iii) Nana (iv) Pica (g) Centre og gravity of solid cone of height h from the vertex of cone is: (i) 1/2(h) (ii) 2/3(h) (iii) 3/4(h) (iv) 1/3(h) (h) The laws of friction are : (i) Two (ii) Three (iii) Four (iv) Five (i) Write the expression for the Lami's theorem. (j) Define the Newton's Second law of Motion. Section - A Marks : 8 Each 2. Define the terms heat and work. What is the differnce between them ? A fluid at a pressure of 3 bar and with a specific volume of 0.18m3/kg contained in a cylinder behind a piston expands reversibly to a pressure of 0.6 bar accordingly to the law p=C/V2 whare C is a constant. Calculate the work done by the fluid on the piston. 3. Derive an expression for the heat -transfer and work done in an isentropic process. Air at 1.02 bar, 22 C, initially occuping a cylinder volume of 0.015 m3 is compressed reversibly and adiabatically by a pitson to a pressure of 6.8 bar. Calculate : (a) The final temperature (b) The final volume (c) The work done 4. The centrifugal pump delivers 50 kg of water per second. The inlet and outlet pressure are 1 ba abd 4.2 bar respectively. The suction is 2.2 m below the centre of pump and delivery is 8.5 m above the center of pump. The suction and dilevry pipe diameters are 20 cm and 10 cm respectively. Determine the capacity of the electric motor to run the pump. 5. Prove that the efficiency of a reversible engine is maximum. (a) A reversible heat pump is used to maintained a tyemperature of 0 C in a refrigeratot, when it rejects the heat to the surronding at 15 C. if the heat removal rate from the refregerator is 1440 kJ/min, determine the COP of the machine and work input required. (b) If the required input to run the pump is developed by a reversible engine which reversis the heat at 380 C and rejects the heat to the atmosphare then determine the overall COP of the system. Section B Marks : 8 Each 6. What is the difference between scalar and vector quantites ? Give the examples of each. A body of 2 kg is fastend to a fixed point by means of a string of length 50 cm. It is acted apon a horijontal force F and rest at a distance of 40 cm from the vertical line throu\gh the fixed point . Find the value of F and tension in the string. 7. define the centre of gravity of body. calculate the moment of inertia about the horizontal and vertical gravity axes (Ixx,Iyy) of the section shown in Fig 8. Define the limiting friction. Two block A and B which are identical weghing W, each are supported by a rod inclined at 45 degree to the horizontal as shownin the fig. If the blocks are in limiting equlibrium, find the coffiient of friction assuming it to be same at both the floor and watt.