## Friday, 3 March 2017

### OBJECTIVE QUESTIONS - Balancing Of Reciprocating masses

Balancing Of Reciprocating masses
Objective type questions

1. The primary unbalanced forces is maximum when the angle of inclination of the crank with the line of stroke is
(a) 0°           (b)  90°
(c) 180°        (d) 360°

2. The partial balancing means
(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. In a locomotive, the ratio of the connecting rod length to the crank radius is kept very large in order to
(a) Minimise the effect of primary forces     (b) Minimise the effect of secondary forces
(c) Have perfect balancing                                 (d) Start the locomotive quickly

5. The swaying couple is maximum or minimum when the angle of inclination of the crank to the line of stroke ( θ ) is equal to
(a) 45° and 135°               (b) 90° and 135°
(c) 135° and 225°             (d) 45° and 225°

6. The tractive force is maximum or minimum when the angle of inclination of the crank to the line of stroke ( θ ) is equal to
(a) 90° and 225°               (b) 135° and 180°
(c) 180° and 225°             (d) 135° and 315°

7. The swaying couple is due to the
(a) Primary unbalanced forces              (b) Secondary unbalanced forces
(c) Two cylinders of locomotive            (d) Partial balancing

8. In a locomotive, the maximum magnitude of the unbalanced force along the perpendicular to the line of stroke, is known as
(a) Tractive force                                      (b) Swaying couple
(c) Hammer blow                                     (d) None of these

9. The effect of hammer blow in a locomotive can be reduced by
(a) Decreasing the speed                (b) Using two or three pairs of wheels coupled together
(c) Balancing whole of the reciprocating parts              (d)  Both (a) and (b)

10. Multi-cylinder engines are desirable because
(a) Only balancing problems are reduced      (b) Only flywheel size is reduced
(c) Both (a) and (b)                                            (d) None of these

11. When the primary direct crank of a reciprocating engine makes an angle with the line of stroke, then the secondary direct crank will make an angle of . . . . . . . with the line of stroke.
(a)  θ/2                   (b)  θ                    (c)  2θ                  (d)  3θ

12. Secondary forces in reciprocating mass on engine frame are

(a) Of same frequency as of primary forces
(b) Twice the frequency as of primary forces
(c) Four times the frequency as of primary forces
(d) None of these

13. The Secondary unbalanced force produced by the reciprocating parts of a certain cylinder of a given engine with crank radius 'r' and connecting rod length 'l' can be considered as equal to primary unbalanced force produced by the same weight having
(a) An equivalent crank radius r2/4and rotating at twice the speed of the engine
(b) r2/4l as equivalent crank radius and rotating at engine speed
(c) Equivalent crank length of r2/4and rotating at engine speed
(d) None of these

14. Which of the statement is correct?
(a) In any engine, 100% of the reciprocating masses can be balanced dynamically
(b) In the case of balancing of multicylinder engine, the value of secondary force is higher than the value of the primary force
(c) In case of balancing of multimass rotating systems, dynamic balancing can be directly
(d) None of these