SATHYABAMA UNIVERSITY
(Established under section 3 of UGC Act,1956)
Course & Branch :B.E - EIE
Title of the Paper :Applied Mechanics Max. Marks :80
Sub. Code :518304/6C0034 Time : 3 Hours
Date :07/05/2010 Session :AN
______
PART - A (10 x 2 = 20)
Answer ALL the Questions
1. Define: Proof Resilience.
2. Define: Strain Energy.
3. State the variation of hoop stress in a thick cylinder.
4. Calculate the torque procedure by a 40HP motor at a frequency of f = 20Hz.
5. What is cohesion in fluids?
6. What is the concept of continuum?
7. What is diffuser type pump?
8. What is meant by total energy line?
9. What is cavitation in turbines? What are the signs of it?
10. What is hydraulic efficiency of a turbine?
PART – B (5 x 12 = 60)
Answer All the Questions
11. Two steel rods one of 80mm diameter and the other of 60mm diameter are joined to end by means of a turn buckle. The other end of each rod is rigidly fixed and there is initially a small tension in the rods. If the effective length of each rod is 4 meters, find the increase in this tension when the turn buckle is turned by one quarter of a turn. On the rod of bigger diameter there are 3 threads per 20mm while there are 4 threads per 20mm on the other rod. Neglect the extension of the turn buckle. Find also what rise in temperature would nullify the increase in tension.
Take
(or)
12. A steel rod 18mm in diameter passes centrally through a steel tube 25mm in internal diameter and 30mm in external diameter. The tube is 750mm long and is closed by rigid washers of negligible thickness and which are fastened by nuts threaded on the rod. The nuts are tightened until the compressive load on the tube is 20kN. Calculate the stresses in the tube and the rod.
Find the increase in these stresses when one nut is tightended by one quarter of a turn relative to the other. There are 4 threads per 10mm. Take E=200kN/mm2.
13. A hollow shaft with diameter ratio 3/5 is required to transmit 450kW at 120 rpm with a uniform twisting moment. The shearing stress in shaft must not exceed 60N/mm2 and the twist in a length of 2.5m must not exceed 1°. Calculate the minimum external diameter of the shaft satisfying these conditions. Take the modulus of rigidity C = 8 x 104N/mm2.
(or)
14. A closed coiled spring having n turns is made of round wire so that the mean diameter D(mm) is 10 times the diameter of the wire. Show that the stiffness in Newton per mm for such a spring is (D/n) x a constant. Determine the value of the constant if the modulus of rigidity of the material is 8.4x104N/mm2. Such a spring is required to support a load of 900 N with an extension of 100mm and a maximum shearing stress of 350N/mm2.
Calculate (i) Its weight (ii) the mean diameter of the coil and (iii) the number of turns. The material weighs 7.75 x 10-5N/mm3
15. A vertical gap 2.2cm wide of infinite extent contains a fluid of viscosity 2.0Ns/m2 and specific gravity 0.9. A metallic plate 1.2mx1.2x0.2cm is to be lifted up with a constant velocity of 0.15m/sec, through the gap. If the plate is in the middle of the gap, find the force required. The weight of the plate is 40N.
(or)
16. The inlet and throat diameter of a horizontal venture meter are 30cm and 10cm respectively. The liquid flowing through the meter is water. The pressure intensity at inlet is 13.734N/cm2 while the vaccum pressure head at the throat is 37cm of mercury. Find the rate of flow. Assume that 4% of the differential head is lost between the inlet and throat. Find also the value of cd for the venture meter.
17. (a) Discuss the important efficiencies of a centrifugal pump. (4)
(b) A centrifugal pump delivers water against a net head of 14.5 meters and a design speed of 1000 rpm. The vanes are curved back to an angle of 30° with the periphery. The impeller diameter is 300mm and outlet width 50mm. Determine the discharge of the pump if manometric efficiency is 95%. (8)
(or)
18. (a) Derive an expression for the discharge through a
reciprocating pump. (4)
(b) A single acting reciprocating pump, running at 50 rpm,
delivers 0.01m3/sec of water.
The diameter of the piston is 200mm and stroke length 400mm. (8)
Determine:
(i) Theoretical discharge of the pump
(ii) co-efficient of discharge, and
(iii) Slip and the percentage slip of the pump.
19. The following data is related to pelton wheel
Head at the base of the nozzle = 80m
Diameter of the jet = 100mm
Discharge of the nozzle = 0.30m3/sec
Power at the shaft = 206kW
Power absorbed in mechanical resistance = 4.5kW
Determine
(a) Power lost in nozzle and
(b) Power lost due to hydraulic resistance in the runner
(or)
20. A conical draft tube having inlet and outlet diameters 1m and 1.5m discharges water at outlet with a velocity of 2.5m/sec. The total length of draft tube is 6m and 1.20m of the length of the draft tube is immersed in water. If the atmospheric pressure head is 10.3m of water and loss of head due to friction in the draft tube is equal to 0.2 x velocity head at outlet of the tube, find
(a) pressure head at inlet, and (b) efficiency of the draft tube.