Set No. 3

Code No: RR10302

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I B.Tech Semester Supplimentary Examinations, June 2009 ENGINEERING MECHANICS ( Common to Mechanical Engineering, Mechatronics, Metallurgy & Material Technology, Production Engineering, Aeronautical Engineering and Automobile Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ????? [16]

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1. Determine the tensions in wires AB, AC and AD,{As shown in Figure 1}.

Figure 1

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2. (a) A short semicircular right cylinder of radius ‘r’ and weight ‘w’ rests on a horizontal surface and is pulled at right angles to its geometric axis by a horizontal force applied at the middle B of the front edge. Find the angle ‘α’ that the flat face will make with the horizontal plane just before sliding begins if the coefficient of friction at the line of contact A is µ . The gravity force ‘W’ must be considered as acting at the center of gravity ‘C’ as shown is the figure2a.

Figure 2a (b) The mean diameter of the threads of a square – threaded screw is 50 mm. The pitch of the thread is 6 mm. The coefficient of friction µ = 0.15. What force must be applied at the end of a 600 mm lever, which is perpendicular to the longitudinal axis of the screw to raise a load of 17.5 kN to lower the load. [10+6] 1 of 3

Set No. 3

Code No: RR10302

3. A laminated belt 9 mm thick and 125 mm broad drives a pulley of 1.2 m diameter at 180 r.p.m the angle of lap being 1900 . The weight of the belt material is 1.16kg/m3 , the friction coefficient between the belt and the pulley is 0.3. If the stress in the belt is not to exceed 1.75N/mm2 Determine:

(b) The power transmitted considering the centrifugal tension. 4. (a) Explain the terms:

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i. Moment of inertia ii. Polar moment of inertia iii. Product of inertia.

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(a) The power transmitted, neglecting the centrifugal tension effect,

[6+10]

Figure 4b

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(b) Locate the centroid of the shaded area as shown in the Figure4b.

5. A cylinder of diameter 500 mm and height 1200 mm has mass density of 8000 kg/m3 . Find out the mass moment of inertia of the cylinder (a) with respect to the axis of the cylinder and

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(b) about a line which coincides with an end face of the cylinder and passing through the centre of this face. [16]

6. (a) A particle under a constant deceleration is moving in a straight line and covers a distance of 20 m in first two seconds and 40 m in the next 5 seconds. Calculate the distance it covers in the subsequent 3 seconds and the total distance covered, before it comes to rest. (b) Deduce the general expression to determine the maximum height and horizontal range of projectile. [8+8]

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Set No. 3

Code No: RR10302

Figure 7

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7. If Wa :Wb :Wc is in the ratio of 3:2:1 , find the accelerations of the blocks A, B, and C. Assume that the pulleys are weightless. {As shown in the Figure7}. [16]

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8. The circular disc shown in the figure8 has a radius r=150 mm and weight of 225 N. The observed frequency of torsional vibration is 1 oscillation/sec. When another body is attached to the same shaft the observed frequency of torsional vibration is 1.2 oscillations/sec. Find the moment of inertia of the second body with respect to the axis of the shaft. [16]

Figure 8

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