# Engineering Mechanics – Section 2

41. The center of gravity of a trapezium with parallel sides a and b lies at a distance of y from the base b, as shown in the below figure. The value of y is 42. A machine having an efficiency of less than 50%, is known as

A. reversible machine
B. non-reversible machine
C. neither reversible nor non-reversible machine
D. ideal machine

43. The total momentum of a system of masses (i. e. moving bodies) in any one direction remains constant unless acted upon by an external force in that direction. This statement is called

A. Newton’s first law of motion
B. Newton’s second law of motion
C. principle of conservation of energy
D. principle of conservation of momentum

Correct Answer: D. principle of conservation of momentum

44. The velocity ratio of a differential pulley block with D and d as the diameters of larger and smaller pulley is 45. The unit of mass moment of inertia in S.I. units is kg-m2
.
A. True
B. False

46. The center of gravity of  an isosceles triangle with base (p) and sides (q) from its base is 47. A newton is defined as the force while acting upon a mass of one kg, produces an acceleration of 1 m / s2 in the direction of which it acts.

A. Yes
B. No

48. The acceleration of a particle moving with simple harmonic motion, at any instant is given by

A. ω.y
B. ω2.y
C. ω2 /y
D. ω3.y