RBI Assistant - Engineering Mechanics 1000+ MCQ [Solved] PDF Download

1. The efficiency of a screw jack is maximum, when (where ? = Helix angle, and ? = Angle of friction.)
A. ? = 45° + ?/2
B. ? = 45° - ?/2
C. ? = 90° + ?
D. ? = 90° - ?
Answer : B

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

3. The centre of gravity of an isosceles triangle with base (p) and sides (q) from its base is
A. [?(4p² - q²)]/6
B. (4p² - q²)/6
C. (p² - q²)/4
D. (p² + q²)/4
Answer : A

4. 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 kinetic energy of translation
D. None of these
Answer : A

5. When the lift is moving upwards with some acceleration, the pressure exerted by a man is __________ to its acceleration.
A. Directly proportional
B. Inversely proportional
C. Cube root
D. None of these
Answer : A

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

7. The moment of inertia of a sphere of mass m and radius r, about an axis tangential to it, is
A. 2mr²/3
B. 2mr²/5
C. 7mr²/3
D. 7mr²/5
Answer : D

8. 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

9. A redundant frame is also called __________ frame.
A. Perfect
B. Imperfect
C. Deficient
D. None of these
Answer : B

10. 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

11. In order to double the period of simple pendulum, the length of the string should be
A. Halved
B. Doubled
C. Quadrupled
D. None of these
Answer : C

12. The minimum force required to slide a body of weight W on a rough horizontal plane is
A. W sin?
B. W cos?
C. W tan?
D. None of these
Answer : C

13. The moment of inertia of a solid sphere of mass m and radius r is
A. 2mr²/3
B. 2mr²/5
C. mr²
D. mr²/2
Answer : B

14. The unit of force in S.I. system of units is
A. Dyne
B. Kilogram
C. Newton
D. Watt
Answer : C

15. The centre of percussion of the homogeneous rod of length L suspended at the top will be
A. L/2
B. L/3
C. 3L/4
D. 2L/3
Answer : D

16. 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

17. A particle inside a hollow sphere of radius r, having coefficient of friction ? can rest up to height of
A. r/2
B. r/A
C. r/3
D. 0.134 r
Answer : D

18. For a self locking machine, the efficiency must be
A. Equal to 50 %
B. Less than 50 %
C. Greater than 50 %
D. 100 %
Answer : B

19. Lami's theorem states that
A. Three forces acting at a point will be in equilibrium
B. Three forces acting at a point can be represented by a triangle, each side being proportional to force
C. If three forces acting upon a particle are represented in magnitude and direction by the sides of a triangle, taken in order, they will be in equilibrium
D. If three forces acting at a point are in equilibrium, each force is proportional to the sine of the angle between the other two
Answer : D

20. The time of flight (t) of a projectile on a horizontal plane is given by
A. t = 2u. sin?/g
B. t = 2u. cos?/g
C. t = 2u. tan?/g
D. t = 2u/g.sin?
Answer : A

21. If a number of forces are acting at a point, their resultant will be inclined at an angle ? with the horizontal, such that
A. tan? = ?H/?V
B. tan? = ?V/?H
C. tan? = ?V × ?H
D. tan? = ?(?V + ?H)
Answer : B

22. The friction xperienced by a body, when at rest, is known as
A. Static friction
B. Dynamic friction
C. Limiting friction
D. Coefficient of friction
Answer : A

23. Two non-collinear parallel equal forces acting in opposite direction
A. Balance each other
B. Constitute a moment
C. Constitute a couple
D. Constitute a moment of couple
Answer : C

24. The centre of gravity of a triangle lies at the point of
A. Concurrence of the medians
B. Intersection of its altitudes
C. Intersection of bisector of angles
D. Intersection of diagonals
Answer : A

25. 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

26. The acceleration of a particle moving with simple harmonic motion, at any instant is given by
A. ?.y
B. ?².y
C. ?²/y
D. ?³.y
Answer : B

27. Which of the following is a vector quantity?
A. Energy
B. Mass
C. Momentum
D. Angle
Answer : C

28. Three forces acting on a rigid body are represented in magnitude, direction and line of action by the three sides of a triangle taken in order. The forces are equivalent to a couple whose moment is equal to
A. Area of the triangle
B. Twice the area of the triangle
C. Half the area of the triangle
D. None of these
Answer : B

29. Forces are called concurrent when their lines of action meet in
A. One point
B. Two points
C. Plane
D. Perpendicular planes
Answer : A

30. 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

31. The C.G. of a right circular solid cone of height h lies at the following distance from the base
A. h/2
B. J/3
C. h/6
D. h/4
Answer : D

32. The unit of work or energy in S.I. units is
A. Newton
B. Pascal
C. Watt
D. Joule
Answer : D

33. Two balls of equal mass and of perfectly elastic material are lying on the floor. One of the balls with velocity v is made to strike the second ball. Both the balls after impact will move with a velocity
A. v
B. v/2
C. v/4
D. v/8
Answer : B

34. The velocity ratio for the first system of pulleys is (where n is the number of pulleys.)
A. n
B. n²
C. 2n
D. 2n - 1
Answer : C

35. Static friction is always __________ dynamic friction.
A. Equal to
B. Less than
C. Greater than
D. None of these
Answer : C

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

37. The unit of moment of inertia of an area is
A. kg-m²
B. kg-m-s²
C. kg/m²
D. m⁴
Answer : D

38. The force required to move the body up the plane will be minimum if it makes an angle with the inclined plane __________ the angle of friction.
A. Equal to
B. Less than
C. Greater than
D. None of these
Answer : A

39. When two elastic bodies collide with each other,
A. The two bodies will momentarily come to rest after collision
B. The two bodies tend to compress and deform at the surface of contact
C. The two bodies begin to regain their original shape
D. All of the above
Answer : D

40. A body will begin to move down an inclined plane if the angle of inclination of the plane is _________ the angle of friction.
A. Equal to
B. Less than
C. Greater than
D. None of these
Answer : C

41. The principle of transmissibility of forces states that, when a force acts upon a body, its effect is
A. Same at every point on its line of action
B. Different at different points on its line of action
C. Minimum, if it acts at the centre of gravity of the body
D. Maximum, if it acts at the centre of gravity of the body
Answer : C

42. 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

43. The maximum mechanical advantage of a lifting machine is
A. 1 + m
B. 1 - m
C. 1 / m
D. m
Answer : C

44. The range of projectile (R) on an upward inclined plane is
A. g. cos² ?/2u². sin (? + ?). cos ?
B. 2u². si (? + ?). cos ?/g. cos² ?
C. g. cos² ?/2u². sin (? - ?). cos ?
D. 2u². sin (? - ?). cos ?/g. cos² ?
Answer : D

45. Effect of a force on a body depends upon
A. Magnitude
B. Direction
C. Position or line of action
D. All of the above
Answer : D

46. 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

47. The moment of inertia of a rectangular section 3 cm wide and 4 cm deep about X-X axis is
A. 9 cm⁴
B. 12 cm⁴
C. 16 cm⁴
D. 20 cm⁴
Answer : C

48. The force applied on a body of mass 100 kg to produce an acceleration of 5 m/s², is
A. 20 N
B. 100 N
C. 500 N
D. None of these
Answer : C

49. Varingon's theorem of moments states that if a number of coplanar forces acting on a particle are in equilibrium, then
A. Their algebraic sum is zero
B. Their lines of action are at equal distances
C. The algebraic sum of their moments about any point in their plane is zero
D. The algebraic sum of their moments about any point is equal to the moment of their resultant force about the same point.
Answer : D

50. If the number of pulleys in a system is equal to its velocity ratio, then it is a __________ system of pulleys
A. First
B. Second
C. Third
D. None of these
Answer : B