# 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

Correct Answer: A. 30° 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

Correct Answer: B. less than

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

A. Right
B. Wrong

Correct Answer: A. Right

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

Correct Answer: A. Agree

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

A. True
B. False

Correct Answer: A. True

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

Correct Answer: A. Right

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

Correct Answer: B. 2.22 mm

40. 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. 90° and 180°
B. 45° and 225°
C. 180° and 270°
D. 270° and 360°

Correct Answer: B. 45° and 225°