Download GTU B.Tech 2020 Winter 5th Sem 3151911 Dynamics Of Machinery Question Paper

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Subject Code: 3151911

GUJARAT TECHNOLOGICAL UNIVERSITY

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Instructions:

1. Attempt any FOUR questions out of EIGHT questions.
2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.

Q.1

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1. Define following terms. (03 MARKS)
   1. Degree of freedom
   2. Resonance
   3. Damping ratio
2. Differentiate static balancing and dynamic balancing. (04 MARKS)

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3. A heavy machine, weighing 3000 N, is supported on a resilient foundation. The static deflection of the foundation due to the weight of the machine is found to be 7.5 cm. It is observed that the machine vibrates with an amplitude of 1 cm when the base of the foundation is subjected to harmonic oscillation at the undamped natural frequency of the system with an amplitude of 0.25 cm. Find (07 MARKS)
   1. the damping constant of the foundation,
   2. the dynamic force amplitude on the base, and
   3. the amplitude of the displacement of the machine relative to the base.

Q.2

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1. Define inertia force and inertia couple. State D' Alembert principle. (03 MARKS)
2. Classify types of vibration. (04 MARKS)
3. The crank and connecting rod of a vertical single cylinder gas engine running at 1800 rpm are 60 mm and 240 mm respectively. The diameter of piston is 80 mm and the mass of the reciprocating parts is 1.2 kg. At a point during the power stroke when the piston has moved 20 mm from the top dead center position, the pressure on the piston is 800 kN/m². Determine (07 MARKS)
   1. Net force on the piston
   2. Thrust in the connecting rod
   3. Thrust on the sides of cylinder walls

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   4. Engine speed at which the above values are zero.

Q.3

1. Define following terms. (03 MARKS)
   1. Turning moment diagram
   2. Coefficient of fluctuation of energy regarding flywheel

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   3. Critical or whirling speed of shaft
2. Explain in what way the gyroscopic couple affects the motion of an aircraft while taking a turn. (04 MARKS)
3. Each wheel of a motorcycle is of 600 mm diameter and has a moment of inertia of 1.2 kg.m². The total mass of the motorcycle and the rider is 180 kg and the combined center of mass is 580 mm above the ground level when the motorcycle is upright. The moment of inertia of the rotating parts of the engine is 0.2 kg.m². The engine speed is 5 times the speed of the wheels and is in the same sense. Determine the angle of heel necessary when the motorcycle takes a turn. (07 MARKS)

Q.4

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1. Define following terms. (03 MARKS)
   1. Over damped system
   2. Logarithmic decrement
   3. Under damped system
2. Sketch displacement vs time graph showing over damped, critically damped and under damped vibration system. (04 MARKS)

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3. Derive formula for natural frequency of the system shown in Figure 1. Assume the pulleys to be frictionless and of negligible mass. (07 MARKS)
   

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