Balancing of Rotating Masses -- OBJECTIVE TYPE QUESTIONS

Balancing Of Rotating masses

Objective type questions

1. The balancing of Rotating and Reciprocating parts of the engine is necessary when it runs at

(a) Slow speed                                         (b) Medium speed 

(c) High speed                                         (d) No speed

2. Which of statements is true for static balancing of shaft,

(a) The net dynamic forces acting on the shaft is zero           
(b)  The net couple due to dynamic forces acting on the shaft is zero

(c) Both (a) and (b)                          (d) None of the above statements

3. For Dynamic balancing of shaft,

(a) The net dynamic forces acting on the shaft is zero           
(b)  The net couple due to dynamic forces acting on the shaft is zero

(c) Both (a) and (b)                          (d) None of the above statements

4. Which of the following statements is correct about the balancing of a mechanicalsystem?

(a) If it is under Static balance, then there will be dynamic balance too           
(b)  If it is under Dynamic balance, then there will be Static balance too

(c) Both Dynamic and Static balance have to be achieved separately
(d) None of the above mentioned statements

5. A distributing mass m₁ attached to a rotating shaft may be balanced by a single mass m₂ attached in the same plane of ratation as that of m₁ such that 

(a) m₁.r₂ = m₂.r₁           
(b)  m₁.r₁ = m₂.r₂

(c) m₁. m₂ = r₁.r₂

6. Which of the following statements are associated inorder to have a complete balancing of the several revolving masses in different planes 

(a) The resultant couple must be zero           
(b) The resultant force must be zero

(c) Both resultant force and couple must be zero
(d) None of the above

7. Which of the following statements are associated with complete dynamic balancing of rotating systems? 

(1) The resultant couple due to all inertia forces is zero           
(2) The support reactions due to forces are zero but not due to couples

(3) The system is automatically statically balanced
(4) Centre of masses of the system lies on the axis of rotation

(a) 1, 2 and 3 only           (b) 2, 3 and 4 only

(c) 1, 3 and 4 only           (d) 1, 2, 3 and 4 

OBJECTIVE QUESTIONS - Longitudinal and Transverse Vibrations

Longitudinal and Transverse Vibrations

Objective type questions

1. When there is a reduction in amplitude over every cycle of vibration, then the body is said to have

(a) Free vibration          (b) Forced vibration          (c) Damped vibration

2. Longitudinal vibrations are said to occur when the particles of a body moves

(a) Perpendicular to axis 

(b) Parallel to its axis 

(c) In a circle about the axis

3. When a body is subjected to transverse vibrations, the stress induced in a body will be

(a) Shear stress          (b) Tensile stress          (c) Compressive stress

4. The factor which affects the critical speed of the shaft is

(a) Diametre of the shaft               (b) Span of the shaft  

(c) Eccentricity                               (d) All of these

5. The ratio of the maximum displacement of the forced vibration to the deflection due to the static force, is known as

(a) Damping factor               (b) Damping coefficient 

(c) Logarithmic decrement  (d) Magnification factor

6. In vibration isolation system, if  ω/ω_n is less than Sqare root 2, then for all values of the damping factor, the transmissibility will be 

(a) Less than unity (b) Equal to unity (c) Greater than unity (d) Zero

Where ω = Circular frequency of the system in rad/s, and 

            ω_n = Natural circular frequency of vibration of the system in rad/s

7. In vibration isolation system, if ω/ω_n is greater than 1, then the phase difference between the transmitted force and the disturbing force is 

(a) 0°           (b)  90°

(c) 180°        (d) 270° 

Open-Loop Transfer Function

Open-Loop Transfer Function

          The open loop transfer function is defined as the overall transfer function of the forward path elements. Consider an open loop control system consisting of several elements having individual transfer function such F₁(D), F₂(D), F₃ (D)  as shown on in Fig.,  

Fig. Open loop control system.

 Thus

                                    = F1 (D ) X F2 (D ) X F3 (D ) = KG (D)

The simplified block diagram of the open loop transfer function is shown in Fig.,

Fig. Simplified open loop control system.

EXERCISES

EXERCISES

1. Define the following terms: 

         (a) Response    (b) Process control     (c) Process Controller

         (d) Regulator   (e) Transducer             (f) Feedback

2. Explain different types of Automatic Control Systems? Explain with an example. 

3. Discuss the importance of block diagrams in control systems. 

4. Draw the block diagrams for the following control systems: 

      (a) A simple carburettor, 

      (b) A thermostatically controlled electric furnace. 

5. What is a transfer function ? 

6. Derive Open - loop and closed - loop transfer functions?

Objective type questions

Automatic Control

Objective type questions

1. The device which is used to keep the variable at a constant desired value is called a  

(a) amplifier                   (b) regulator

(C) deviation sensor     (d) process controlled

2. A simple Bourdon tube pressure gauge is a

(a) closed-loop control system 

(b) manually operated system 

(c) open-loop control system

(d) none of the above 

3. The transfer function of a 4 to 1 reduction gear box is

(a) 2          (b) 1/4 

(c) 4          (d) 1/2

 4. The overall transfer function of three blocks connected in series is 

(a) {F1 ( D ) X F2 ( D)}/F3 ( D)          (b) {F1 ( D ) X F3( D)}/F2 (D)

(c)  F1 ( D ) X F2 ( D ) X F3( D)          (d)  1 / {F1 ( D ) X F2 ( D ) X F3 ( D)}