JNTU
JNTU B.Tech II KINEMATICS OF MACHINERY Previous Question Paper (March - 2021 - R16)
Answer any five questions
All questions carry equal marks
Main
What is machine? Giving example, differentiate between a machine and a structure.
Answer
A machine is a mechanism or collection of mechanisms that receives energy in some available form and transforms it into some useful work. It consists of a number of resistant bodies (links) arranged such that they transmit definite motion to each other. An example is an internal combustion engine, which converts chemical energy into mechanical work.
The difference between a machine and a structure is as follows:
- Machine: The parts are designed to move relative to each other to transmit motion and perform work. It transforms energy.
- Structure: The parts are designed to carry loads without any relative motion between them. It does not perform work or transform energy; for example, a bridge or a roof truss.
Write notes on complete and incomplete constraints in lower and higher pairs, illustrating your answer with neat sketches.
Answer
Constraints define the relative motion between two links in a pair.
- Completely Constrained Motion: Occurs when the motion between a pair is limited to a definite direction, regardless of the direction of the force applied. For example, a square bar in a square hole or a shaft with collars in a circular bearing.
- Incompletely Constrained Motion: Occurs when the motion between a pair can take place in more than one direction. For example, a circular shaft in a circular hole; the shaft can both rotate and slide axially.
Lower pairs (like a journal bearing) provide surface contact, whereas higher pairs (like a cam and follower) provide point or line contact. Incomplete constraints in higher pairs are common, such as a wheel rolling on a flat surface, where the wheel can roll and slide simultaneously unless constrained by external forces.
Classify and explain the Kinematic pairs.
Answer
Sign in to view the complete answer paper.
Sketch and explain any two inversions of a double slider crank chain.
Answer
Sign in to view the complete answer paper.
Show that slider crank mechanism is a modification of the basic four bar mechanism.
Answer
Sign in to view the complete answer paper.
Draw the acceleration diagram of slider crank mechanism.
Answer
Sign in to view the complete answer paper.
In a four-bar chain ABCD, the link AD is fixed and the crank AB rotates at 10 radians per second clock wise. Lengths of the links are AB=60mm, BC=CD=70mm, DA=120mm. When angle DAB=60 degrees and both B and C lie on the same side of AD, find angular velocities and angular accelerations of BC and CD.
Answer
Sign in to view the complete answer paper.
What is Coriolis component of acceleration? How is it determined?
Answer
Sign in to view the complete answer paper.
Explain the procedure to determine the velocity and acceleration of a slider crank mechanism by Klein’s construction.
Answer
Sign in to view the complete answer paper.
Explain why two Hooke’s joints are used to transmit motion from the engine to the differential of an automobile.
Answer
Sign in to view the complete answer paper.
The angle between the axes of two shafts connected by Hooke’s joint is 18 degrees. Determine the angle turned through by the driving shaft when the velocity ratio is maximum and unity.
Answer
Sign in to view the complete answer paper.
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 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 a uniform velocity of 120 rpm and has a least radius of 20 mm. What will be the maximum velocity and acceleration of the follower during the lift and the return?
Answer
Sign in to view the complete answer paper.
What is Tangent cam? Derive the expressions for the velocity and acceleration of a roller follower in the tangent cam.
Answer
Sign in to view the complete answer paper.
A 20 degree-pinion having 24 teeth drives a gear wheel of 56 teeth. The module is 5 mm and they are of standard full depth. Determine (i) path of approach (ii) path of recess and (iii) contact ratio.
Answer
Sign in to view the complete answer paper.
With a neat sketch explain the principle and operation of the pre-selective gear box of an automobile. Discuss about the velocity ratios and the selection of number of teeth on various gears.
Answer
Sign in to view the complete answer paper.