JNTU
JNTU B.Tech II KINEMATICS OF MACHINERY Previous Question Paper (December - 2017 - R13)
Note: This question paper contains two parts A and B. Part A is compulsory which carries 25 marks. Answer all questions in Part A. Part B consists of 5 Units. Answer any one full question from each unit.
Part A
Define mechanical advantage and transmission angle of a mechanism.
Answer
Mechanical Advantage is the ratio of the output force (or torque) to the input force (or torque) in a mechanism. The Transmission Angle is the acute angle between the output link and the coupler link of a four-bar mechanism, which determines the effectiveness of force transmission.
What is a kinematic pair? Classify kinematic pairs according to nature of relative motion.
Answer
A Kinematic Pair is a joint of two links having relative motion between them. They are classified based on the nature of relative motion as:
- Sliding pair (e.g., piston and cylinder)
- Turning pair (e.g., crankshaft in a bearing)
- Rolling pair (e.g., ball bearings)
- Screw pair (e.g., nut and bolt)
- Spherical pair (e.g., ball and socket joint)
Name all the inversions of slider-crank mechanism with one application for each Inversion.
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Briefly explain about coriolis acceleration component.
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What is scott-russel mechanism? What is its limitation?
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Briefly explain Ackermann steering gear.
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Define base circle, pitch circle and pressure angle for cams.
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What is undercutting in cams? Explain.
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What type of gears are used for intersecting shafts? Explain.
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What is the difference between simple and compound gear trains?
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Part B
What are the inversions of a four bar chain? Explain in detail.
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A crank-rocker mechanism has a 60 mm fixed link, a 30mm crank, 50mm coupler and a 60 mm rocker. Draw the mechanism and determine the maximum and minimum transmission angles.
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What are different types of constrained motion? Explain them in detail.
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The length of a fixed link of a crank and slotted-lever mechanism is 250 mm and that of crank is 100 mm. Determine the Inclination of the slotted lever with the vertical in the extreme position and also find the quick-return ratio.
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Define instantaneous centre of rotation. State and prove Kennedy’s theorem as applicable to instantaneous centres of rotation of three bodies.
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In a slider crank mechanism, the lengths of the crank and the connecting rod are 200 mm and 800mm respectively. When the crank has turned 30 degrees from its inner dead centre and it rotates at 40 rad/sec, find the velocity of slider.
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For the configuration of a slider-crank mechanism shown in the figure 1, calculate the:
- Acceleration of the slider B
- Acceleration of the point E
- Angular acceleration of the link AB, OA rotates at 20rad/s CCW.
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Enumerate straight-line mechanisms. Why are they classified into exact and approximate straight-line mechanisms? Sketch all the mechanisms.
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Sketch a paucellier mechanism. Prove that it can be used to trace a straight line.
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What is an automobile steering gear? What are its types? Which steering gearing is preferred and why?
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Derive an expression for the ratio of angular velocities of the shafts of a hooke’s joint.
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Draw the profile of a cam operating a knife-edge follower having a lift of 30 mm the cam raises the follower with SHM for 150 degrees of the rotation followed by a period of dwell for 60 degrees. The follower descends for the next 100 degrees rotation of the cam with uniform velocity again followed by a dwell period. The cam rotates at uniform velocity of 120 rpm and has a least radius of 20mm.
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What is a follower? Discuss about different types of followers.
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Deduce the expressions for the velocity and acceleration of the follower when it moves with simple harmonic motion.
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Discuss the various terms used in gear terminology and explain them with a neat sketch.
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Derive expressions for arc of contact of pinion and gear with a neat sketch.
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What is meant by interference in involute gears? Explain.
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Below figure 2 shows a gear train in which gears D-E and F-G are compound gears. D gears with F; and G gears with C. the numbers of teeth on each gear are A=30 B=120, C=135, D=30, E=75, F=30, G=60. If the wheel A is fixed and the arm makes 20 revolutions clockwise, find the revolutions of B and C.
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