RRB NTPC - Engineering Mechanics 1000+ MCQ [Solved] PDF Download

1. A trolley wire weighs 1.2 kg per meter length. The ends of the wire are attached to two poles 20 meters apart. If the horizontal tension is 1500 kg find the dip in the middle of the span
A. 2.5 cm
B. 3.0 cm
C. 4.0 cm
D. 5.0 cm
Answer : C

2. If a rigid body is in equilibrium under the action of three forces, then
A. These forces are equal
B. The lines of action of these forces meet in a point
C. The lines of action of these forces are parallel
D. Both (B) and (C) above
Answer : D

3. On a ladder resting on smooth ground and leaning against vertical wall, the force of friction will be
A. Towards the wall at its upper end
B. Away from the wall at its upper end
C. Upwards at its upper end
D. Downwards at its upper end
Answer : C

4. The bellow figure shows the two equal forces at right angles acting at a point. The value of force R acting along their bisector and in opposite direction is
A. P/2
B. 2P
C. ?2 × P
D. P/?2
Answer : C

5. The product of either force of couple with the arm of the couple is called
A. Resultant couple
B. Moment of the forces
C. Resulting couple
D. Moment of the couple
Answer : D

6. Which of the following statement is correct in connection with projectiles?
A. A path, traced by a projectile in the space, is known as trajectory.
B. The velocity, with which a projectile is projected, is known as the velocity of projection.
C. The angle, with the horizontal, at which a projectile is projected, is known as angle of projection.
D. All of the above
Answer : D

7. The centre 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
A. h [(2a + b)/(a + b)]
B. (h/2) [(2a + b)/(a + b)]
C. (h/3) [(2a + b)/(a + b)]
D. (h/3) [(a + b)/(2a + b)]
Answer : C

8. A block of mass m1, placed on an inclined smooth plane is connected by a light string passing over a smooth pulley to mass m2, which moves vertically downwards as shown in the below figure. The tension in the string is
A. m₁/m₂
B. m₁. g. sin ?
C. m₁.m₂/m₁ + m₂
D. m₁. m₂.g (1 + sin ?)/(m₁ + m₂)
Answer : D

9. In order to completely specify angular displacement by a vector, it must fix
A. Direction of the axis of rotation
B. Magnitude of angular displacement
C. Sense of angular displacement
D. All of these
Answer : D

10. The velocity ratio for the third system of pulleys is
A. n
B. n²
C. 2n
D. 2n - 1
Answer : D

11. Dynamic friction as compared to static friction is
A. Same
B. More
C. Less
D. May be less of more depending on nature of surfaces and velocity
Answer : C

12. A couple produces
A. Translatory motion
B. Rotational motion
C. Combined translatory and rotational motion
D. None of the above
Answer : B

13. The range of a projectile is maximum, when the angle of projection is
A. 30°
B. 45°
C. 60°
D. 90°
Answer : B

14. One end of a helical spring is fixed while the other end carries the load W which moves with simple harmonic motion. The frequency of motion is given by (where ? = Deflection of the spring.)
A. 2?. ?(g/?)
B. 1/2?. ?(g/?)
C. 2?. ?(?/g)
D. 1/2?. ?(?/g)
Answer : B

15. The unit of angular velocity is
A. m/min
B. rad/s
C. Revolutions/min
D. Both (B) and (C)
Answer : D

16. The forces, whose lines of action are parallel to each other and act in the same directions, are known as
A. Coplanar concurrent forces
B. Coplanar non-concurrent forces
C. Like parallel forces
D. Unlike parallel forces
Answer : C

17. A pair of smith's tongs is an example of the lever of
A. Zeroth order
B. First order
C. Second order
D. Third order
Answer : C

18. The resultant of two forces P and Q acting at an angle ? is
A. ?(P² + Q² + 2PQ sin?)
B. ?(P² + Q² + 2PQ cos?)
C. ?(P² + Q² - 2PQ cos?)
D. ?(P² + Q² - 2PQ tan?)
Answer : B

19. If the resultant of two equal forces has the same magnitude as either of the forces, then the angle between the two forces is
A. 30°
B. 60°
C. 90°
D. 120°
Answer : D

20. The motion of a wheel of a car is
A. Purely translation
B. Purely rotational
C. Combined translation and rotational
D. None of these
Answer : C

21. Moment of inertia of a triangular section of base (b) and height (h) about an axis passing through its vertex and parallel to the base, is __________ than that passing through its C.G. and parallel to the base.
A. Nine times
B. Six times
C. Four times
D. Two times
Answer : A

22. Frictional force encountered after commencement of motion is called
A. Limiting friction
B. Kinematic friction
C. Frictional resistance
D. Dynamic friction
Answer : D

23. During elastic impact, the relative velocity of the two bodies after impact is __________ the relative velocity of the two bodies before impact.
A. Equal to
B. Equal and opposite to
C. Less than
D. Greater than
Answer : B

24. The term 'Centroid' is
A. The same as centre of gravity
B. The point of suspension
C. The point of application of the resultant of all the forces tending to cause a body to rotate about a certain axis
D. None of the above
Answer : A

25. One watt is equal to
A. 0.1 joule/s
B. 1 joule/s
C. 10 joules/s
D. 100 joules/s
Answer : B

26. Moment of inertia is the
A. Second moment of force
B. Second moment of area
C. Second moment of mass
D. All of these
Answer : D

27. If rain is falling in the opposite direction of the movement of a pedestrian, he has to hold his umbrella
A. More inclined when moving
B. Less inclined when moving
C. More inclined when standing
D. Less inclined when standing
Answer : D

28. In actual machines
A. Mechanical advantage is greater than velocity ratio
B. Mechanical advantage is equal to velocity ratio
C. Mechanical advantage is less than velocity ratio
D. Mechanical advantage is unity
Answer : C

29. If the masses of both the bodies, as shown in the below figure, are doubled, then the acceleration in the string will be
A. Same
B. Half
C. Double
D. None of these
Answer : A

30. A circular hole of 50 mm diameter is cut out from a circular disc of 100 mm diameter as shown in the below figure. The centre of gravity of the section will lie
A. In the shaded area
B. In the hole
C. At O
D. None of these
Answer : A

31. Moment of inertia of a rectangular section having width (b) and depth (d) about an axis passing through its C.G. and parallel to the depth (d), is
A. db³/12
B. bd³/12
C. db³/36
D. bd³/36
Answer : A

32. The loss of kinetic energy during inelastic impact, is given by (where m₁ = Mass of the first body, m₂ = Mass of the second body, and u₁ and u₂ = Velocities of the first and second bodies respectively.)
A. [m? m?/2(m? + m?)] (u? - u?)²
B. [2(m? + m?)/m? m?] (u? - u?)²
C. [m? m?/2(m? + m?)] (u?² - u?²)
D. [2(m? + m?)/m? m?] (u?² - u?²)
Answer : A

33. The C.G. of a plane lamina will not be at its geometrical centre in the case of a
A. Right angled triangle
B. Equilateral triangle
C. Square
D. Circle
Answer : A

34. Which of the following is an equation of linear motion? (where, u and v = Initial and final velocity of the body, a = Acceleration of the body, and s = Displacement of the body in time t seconds.)
A. v = u + a.t
B. s = u.t + ½ a.t²
C. v² = u² + 2a.s
D. All of these
Answer : D

35. The periodic time of one oscillation for a simple pendulum is (where l = Length of the pendulum.)
A. (1/2?). ?(l/g)
B. (1/2?). ?(g/l)
C. 2?. ?(l/g)
D. None of these
Answer : C

36. A machine having an efficiency less than 50%, is known as
A. Reversible machine
B. Non-reversible machine
C. Neither reversible nor non-reversible machine
D. Ideal machine
Answer : B

37. The velocity ratio of a differential pulley block with D and d as the diameters of larger and smaller pulley, is
A. D/(D - d)
B. D/(D + d)
C. 2D/(D - d)
D. 2D/(D + d)
Answer : C

38. 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
Answer : B

39. The velocity of a body on reaching the ground from a height h, is
A. 2.?(gh)
B. ?(gh)
C. ?(2gh)
D. 2g.?h
Answer : C

40. The rate of doing work is known as
A. Potential energy
B. Kinetic energy
C. Power
D. None of these
Answer : C

41. The maximum efficiency o a screw jack is
A. (1 - sin?)/(1 + sin?)
B. (1 + sin?)/(1 - sin?)
C. (1 - tan?)/(1 + tan?)
D. (1 + tan?)/(1 - tan?)
Answer : A

42. If two bodies having masses m₁ and m₂ (m₁>m₂) have equal kinetic energies, the momentum of body having mass m₁ is _________ the momentum of body having mass m₂.
A. Equal to
B. Less than
C. Greater than
D. None of these
Answer : C

43. The angle which an inclined plane makes with the horizontal when a body placed on it is about to move down is known as angle of
A. Friction
B. Limiting friction
C. Repose
D. Kinematic friction
Answer : C

44. Mass moment of inertia of a thin rod about its one end is __________ the mass moment of inertia of the same rod about its midpoint
A. Same as
B. Twice
C. Thrice
D. Four times
Answer : D

45. The periodic time of a particle with simple harmonic motion is __________ proportional to the angular velocity.
A. Directly
B. Inversely
C. Square root
D. None of these
Answer : B

46. Moment of inertia of a hollow rectangular section as shown in the below figure about X-X axis, is
A. (BD³/12) - (bd³/12)
B. (DB³/12) - (db³/12)
C. (BD³/36) - (bd³/36)
D. (DB³/36) - (db³/36)
Answer : A

47. The centre of gravity of a quadrant of a circle lies along its central radius (r) at a distance of
A. 0.5r
B. 0.6 r
C. 0.7 r
D. 0.8 r
Answer : B

48. The algebraic sum of the resolved parts of a number of forces in a given direction is equal to the resolved part of their resultant in the same direction. This is known as
A. Principle of independence of forces
B. Principle of resolution of forces
C. Principle of transmissibility of forces
D. None of these
Answer : B

49. Moment of inertia of a hollow circular section, as shown in the below figure about an axis perpendicular to the section, is __________ than that about X-X axis.
A. Two times
B. Same
C. Half
D. None of these
Answer : A

50. The C.G. of a solid hemisphere lies on the central radius 3r
A. At distance from the plane base 3r
B. At distance from the plane base 3r
C. At distance from the plane base 3r
D. At distance from the plane base
Answer : D