JNTU
JNTU B.Tech II KINEMATICS OF MACHINES Previous Question Paper (May - 2019 - R15)
Part A is compulsory. Answer all questions in Part A. Part B consists of 5 Units. Answer any one full question from each unit.
Part A
How linkages, mechanism and structures are obtained.
Answer
A linkage is formed by connecting rigid bodies (links) with joints. If the linkage is constrained such that one link is fixed and others move to transmit motion or force, it is a mechanism. If the linkage has zero degrees of freedom, it acts as a structure, which cannot undergo relative motion.
What is the rule to find DOF of a spatial mechanism?
Answer
The degree of freedom (DOF) for a spatial mechanism is determined by the Kutzbach-Grubler criterion for spatial mechanisms:
where n is the total number of links, and j₁ to j₅ represent the number of joints with 1 to 5 degrees of freedom respectively.
What is three centres in line theorem?
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What is centrode and axode in a plane motion of a body?
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Differentiate Davis and Ackermann steering gear mechanism.
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What is a straight line motion mechanism?
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When does the maximum acceleration is attained in SHM during return stroke?
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What are circular arc cam with concave and convex flanks.
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What is law of gearing?
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What is the condition for minimum number of teeth to avoid interference?
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Part B
Describe all the possible in versions of single of a slider crank chain. Give one practical applications for each inversion.
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What is an inversion?
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Find the maximum and minimum transmission angles for the mechanisms as shown in Figure 1.
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The figure 2 shows the mechanism of a pneumatic riveter. The arms AB and BC are each 7 in. long, link BE is 20 in. and link DC 13 in. long. The centre line of the piston is horizontal and 8 in. below A. When AC is vertical, BE makes an angle of 120 with the vertical. Find the velocity ratio between D and the ram E when AC is vertical, and the efficiency of the machine if a load of 2500N on the piston causes a thrust of 5 kN at E.
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A gas engine has a stroke of 425 mm and a connecting rod 1m long. The crankshaft carries two flywheels each of which weights 6kN and has a radius of gyration of 675 mm. When the crank makes an angle of 30 with the idc on the firing stroke, there is an unbalanced turning moment on the crankshaft of 8100N.m in the direction of motion of the crank. If at this instant the angular velocity of the crank is 8.38 rad/s (80 rpm) find the acceleration of the piston and angular acceleration of the connecting rod.
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Sketch and describe the principle of Grasshopper mechanism.
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What is the condition of correct steering of steering gear mechanism.
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Explain the mechanism behind Davis steering gear.
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Explain all terms and label the same in a cam profile.
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What motions are required for a cam with roller oscillating follower?
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Draw the displacement time and velocity time diagrams for a follower in order to satisfy the following conditions. The stroke of the follower is 1 inch. The outward stroke takes place with SHM during 90 of cam rotation and follower stroke with SHM during 75 of cam rotation. The follower is to dwell in the out position for 45 of cam rotation and cam turns at uniform speed of 800 rpm.
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A bevel gear epicyclic is shown in figure 3. The wheel A is keyed to the driving shaft, the wheel F to the driven shaft and the wheel E is fixed. The arm G which supports the inclined shaft is free to turn about the common axis of the driving and the driven shafts, and the wheels B, C & D are keyed to the inclined shaft F, having 74 teeth. Find the speed of F in terms of the speed of A. What is the speed ratio when E has 81 teeth?
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Compare cycloidal and involute tooth forms.
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Derive an expression for arc of contact, and path of contact of pinion gear rack arrangement.
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