JNTU
JNTU B.Tech II KINEMATICS OF MACHINES Previous Question Paper (May - 2019 - 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. Each question carries 10 marks and may have a, b, c as sub questions.
Part A
How linkages, mechanism and structures are obtained.
Answer
A linkage is formed by connecting a number of rigid bodies (links) by joints. A mechanism is obtained when one of the links of a kinematic chain is fixed, allowing for constrained motion between the remaining links to transform motion or force. A structure is obtained when the links are connected in such a way that no relative motion is possible between them, resulting in a degree of freedom equal to or less than zero.
What is the rule to find DOF of a spatial mechanism?
Answer
The degrees of freedom (DOF) of a spatial mechanism are determined using the Kutzbach-Grubler criterion for spatial linkages, expressed by the formula:
Where:
- F is the degrees of freedom or mobility of the mechanism.
- n is the total number of links, including the fixed link (frame).
- p_i is the number of lower pairs (joints) having 'i' degrees of freedom, where 'i' ranges from 1 to 5.
Alternatively, the formula is often written as F = 6(n - 1 - j) + Σf_i, where j is the total number of joints and f_i is the degrees of freedom allowed by each individual joint.
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 inversions of a single 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. The figures indicate the dimensions in standard units of length.
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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 deg 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 deg of cam rotation and follower stroke with SHM during 75 deg of cam rotation. The follower is to dwell in the out position for 45 deg 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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