# Theory of Machines – Section 1

31. The gears are termed as medium velocity gears if their peripheral velocity is

A. 1 – 3 m/s
B. 3 – 15 m/s
C. 15 – 30 m/s
D. 30 – 50 m/s

Correct Answer: B. 3 – 15 m/s

32. For a twin cylinder V-engine, the crank positions for primary reverse cranks and secondary direct cranks are shown in the below figure. The engine is a A. 30° V-engine
B. 60° V-engine
C. 120° V-engine
D. 150° V-engine

33. The frequency of damped vibrations with viscous damping is __________ the frequency of undamped vibrations.

A. more than
B. less than
C. same as

34. Whitworth quick return motion mechanism consists of three turning pairs and one sliding pair.

A. Right
B. Wrong

35. The rotor of a ship rotates in the clockwise direction when viewed from the stern and the ship takes a right turn. The effect of the gyroscopic couple acting on it will be to raise the stern and lower the bow.

A. Agree
B. Disagree

36. The sliding pairs, turning pairs and screw pairs form lower pairs.

A. True
B. False

37. When a particle moves round the circumference of a circle of radius r with ω rad/s, then its maximum acceleration is ω2r.

A. Right
B. Wrong

38. The static friction

A. bears a constant ratio to the normal reaction between the two surfaces
B. is independent of the area of contact, between the two surfaces
C. always acts in a direction, opposite to that in which the body tends to move
D. all of the above

Correct Answer: D. all of the above

39. A shaft has an attached disc at the center of its length. The disc has its center of gravity located at a distance of 2 mm from the axis of the shaft. When the shaft is allowed to vibrate in its natural bow-shaped mode, it has a frequency of vibration of 10 rad/s. When the shaft is rotated at 300 r.p.m., it will whirl with a radius of

A. 2 mm
B. 2.22 mm
C. 2.50 mm
D. 3.0 mm