# Theory of Machines – Section 1

41. The pressure angle of a cam is the angle between the direction of the follower motion and a normal to the

A. pitch circle
B. base circle
C. pitch curve
D. prime circle

42. A pair of friction discs is an example of a rolling pair.

A. True
B. False

43. In order to balance the reciprocating masses,

A. primary forces and couples must be balanced
B. secondary forces and couples must be balanced
C. both (a) and (b)
D. none of these

Correct Answer: C. both (a) and (b)

44. In a screw jack, the effort required to lower the load W is given by

A. P = W tan(α – φ)
B. P = W tan(α + φ)
C. P = W tan(φ – α)
D. P = W cos(α + φ)

Correct Answer: C. P = W tan(φ – α)

45. An automobile steering gear is an example of

A. sliding pair
B. rolling pair
C. lower pair
D. higher pair

46. The frictional torque transmitted in a multi-collared shaft is same as that of a single collared shaft.

A. Right
B. Wrong

47. In order to give the primary balance of the reciprocating parts of a multi-cylinder in-line engines,

A. the algebraic sum of the primary forces must be equal to zero
B. the algebraic sum of the couples about any point in the plane of the primary forces must be equal to zero
C. both (a) and (b)
D. none of these

Correct Answer: C. both (a) and (b)

48. The gear train usually employed in clocks is a

A. simple gear train
B. reverted gear train
C. sun and planet gear
D. differential gear

Correct Answer: B. reverted gear train

49. A mass of 1 kg is attached to the end of a spring with a stiffness of 0.7 N/mm. The critical damping coefficient of this system is

A. 1.4 N-s/m
B. 18.52 N-s/m
C. 52.92 N-s/m
D. 529.2 N-s/m