Engineering Mechanics – Section 3

41. For a self-locking machine, the efficiency must be

A. equal to 50%
B. less than 50%
C. greater than 50%
D. 100%

Correct Answer: B. less than 50%

42. The resultant of the two forces P and Q is R. If Q is doubled, the new resultant is perpendicular to P. Then

A. P = Q
B. Q = R
C. Q = 2R
D. none of these

Correct Answer: B. Q = R

43. One joule is equal to

A. 0.1 N-m
B. 1 N-m
C. 10 N-m
D. 100 N-m

Correct Answer: B. 1 N-m

44. Whenever a force acts on a body and the body undergoes a displacement, then

A. work is said to be done
B. power is being transmitted
C. body has a kinetic energy of translation
D. none of these

Correct Answer: A. work is said to be done

45. When a particle moves along a straight path, there will be centripetal acceleration as well as tangential acceleration.

A. Correct
B. Incorrect

Correct Answer: B. Incorrect

46. If the body falls freely under gravity, then the gravitational acceleration is taken as

A. +8.9 m/s2
B. -8.9 m/s2
C. +9.8 m/s2
D. -9.8 m/s2

Correct Answer: C. +9.8 m/s2

47. A framed structure, as shown in the below figure, is a

em-se3-47

A. perfect frame
B. deficient frame
C. redundant frame
D. none of the above

Correct Answer: A. perfect frame

48. The rate of change of displacement of a body is called

A. velocity
B. acceleration
C. momentum
D. none of these

Correct Answer: A. velocity

49. The efficiency of a screw jack is maximum, when(where α = Helix angle, and φ = Angle of friction.)

A. α = 45° + φ/2
B. α = 45° – φ/2
C. α = 90° + φ
D. α = 90° – φ

Correct Answer: B. α = 45° – φ/2

50. The periodic time (T) is given by(where ω = Angular velocity of particle in rad / s.)

A. ω/2π
B. 2π/ω
C. 2π x ω
D. π/ω

Correct Answer: B. 2π/ω

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