www.nptc.ac.in Nachimuthu Polytechnic College : Mechanics Of Materials Model Question Paper

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8201 MECHANICS OF MATERIALS
Model Question Paper

NOTE : 1. Answer all questions . Choosing any one from Part - A (5marks) and one from Part - B (10marks)
2. All Questions carry equal marks.

I. A. i) State Hook’s law and define factor of safety.
ii) Define the properties of ductility and malleability
B i) A Steel bar 2m long 20mm wide and 10mm thick is subjected to a pull
of 20 KN in the direction of its length.Find the changes in length, breath and thickness.Take E = 2OO KN /mm2 & Poisson’s ratio = 0.25.
ii) A Spherical ball of 500mm dia,when subjected to a hydrostatic pressure of 5 Mpa is found to shrink to a ball of 498.8mm dia.If the Poisson’s ratio of the ball is 0.24,find E .

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II. A. i) Distinguish between moment of inertia and polar moment of inertia.
ii) Differentiate between the longitudinal stress and circumferential stress in thin cylinders subjected to internal pressure.
B. i) Find the moment of inertia about the centroidal axes of an angle section 90 x 75 x 20 mm thick with its 90 x 20 mm flange being vertical.
ii) Calculate the increase in volume enclosed by a boiler shell 2.5 long,1m
in diameter when it is subjected to an internal pressure of 150N/mm2. The wall thickness is such that the maximum tensile stress in the shell is 2150 N / mm2 under this pressure, E = 200 KN / mm2 , 1/m = 0.3.

III. A. i) What are the different types of beams.
ii) State any five assumptions made in theory of simple bending.
B. i). A Simply supported beam of length 8m carries a udl of 1KN / m for the entire span. It also carries a point load of 10 KN at its centre.Find out the max deflection of the beam.E=200KN/mm2 and I=200 x 106 mm4.
ii) A timber beam is freely supported on supports 6m apart.It carries a udl of 12KN / m for the entire span and a concentrated load of 9 KN at 3.5 m from the right support.If the stress in timber is not to exceed 8N/mm2 , design a suitable rectangular section with depth equal to twice the breath IV.A.

IV. A. i) What are the advantages of hollow shaft over the solid shaft?
ii) State the assumptions made in theory of pure torsion.
B. i). A hollow circular shaft of external diameter 75 mm and internal diameter 40 mm is to transmit power at a speed of 40 rpm.If the maximum shear stress is not to exceed 80N/mm2. Calculate the power in kW transmitted by the shaft.
ii) Derive expressions for maximum slope and deflection of a simply supported beam with a central point load.
V. A. i) Define Co-efficient of friction,angle of friction and cone of friction.
ii) State the Law of belting.
B. i) In a flat belt the initial tension is 180N.The angle of lap of the smaller pulley is 170º . The co- efficient of friction between the belt and pulley surface is 0.215.Dia of pulley is 900 mm and it runs at 540 rpm. Determine the power that can be transmitted at the above speed. Neglect the effect of centrifugal tension.
ii) In a spur gear arrangement,the power transmitted is 3 kN.The driving pinion has 30 teeth and 40 mm circular pitch.Calculate the speed in rpm for the pinion.If the pressure between the teeth exerted is not to exceed 600 N.