System of Units (SI, MKS, CGS) – Engineering Mechanics MCQs
Q1. The SI unit of force is
A) Dyne
B) Newton
C) Kilogram-force
D) Joule
Answer: B) Newton
Explanation: 1 Newton = 1 kg·m/s² (SI unit of force).
Q2. The CGS unit of force is
A) Newton
B) Dyne
C) Erg
D) Pound
Answer: B) Dyne
Explanation: 1 Dyne = 10⁻⁵ Newton.
Q3. The SI unit of work is
A) Erg
B) Joule
C) Calorie
D) Watt
Answer: B) Joule
Explanation: Work = Force × Distance = N·m = Joule.
Q4. The CGS unit of work is
A) Joule
B) Dyne
C) Erg
D) Newton
Answer: C) Erg
Explanation: 1 Erg = 10⁻⁷ Joule.
Q5. The MKS unit of power is
A) Joule
B) Watt
C) Horsepower
D) Erg
Answer: B) Watt
Explanation: Power = Work/Time = Joule/second = Watt.
Q6. The SI unit of energy is
A) Calorie
B) Joule
C) Erg
D) Electron volt
Answer: B) Joule
Explanation: Energy and work share the same SI unit, Joule.
Q7. The CGS unit of energy is
A) Dyne
B) Erg
C) Joule
D) Newton
Answer: B) Erg
Explanation: 1 Erg = 10⁻⁷ Joule.
Q8. The SI unit of pressure is
A) Pascal
B) Bar
C) Torr
D) Atmosphere
Answer: A) Pascal
Explanation: 1 Pascal = 1 N/m².
Q9. The CGS unit of pressure is
A) Barye
B) Pascal
C) Dyne/cm²
D) Torr
Answer: A) Barye
Explanation: 1 Barye = 1 dyne/cm² = 0.1 Pa.
Q10. The SI unit of velocity is
A) cm/s
B) m/s
C) km/h
D) ft/s
Answer: B) m/s
Explanation: In SI system, distance is measured in meters and time in seconds.
Q11. The SI unit of acceleration is
A) m/s
B) m/s²
C) cm/s²
D) km/h²
Answer: B) m/s²
Explanation: Acceleration = Change in velocity / Time.
Q12. The SI unit of momentum is
A) kg·m/s
B) N·s
C) Both A and B
D) Joule
Answer: C) Both A and B
Explanation: Momentum = mass × velocity = kg·m/s = N·s.
Q13. The CGS unit of momentum is
A) g·cm/s
B) dyne·s
C) erg·s
D) joule·s
Answer: A) g·cm/s
Explanation: Derived from mass in grams and velocity in cm/s.
Q14. The SI unit of angular velocity is
A) rad/s
B) degree/s
C) revolution/s
D) rad/min
Answer: A) rad/s
Explanation: Angular velocity = angle rotated/time.
Q15. The SI unit of torque is
A) N·m
B) Joule
C) Dyne·cm
D) kg·m²/s²
Answer: A) N·m
Explanation: Torque = Force × Perpendicular distance.
Q16. The SI unit of density is
A) g/cm³
B) kg/m³
C) kg/cm³
D) g/m³
Answer: B) kg/m³
Explanation: Density = Mass/Volume.
Q17. The SI unit of pressure energy per unit weight is
A) N·m/kg
B) m
C) J/kg
D) Pa
Answer: B) m
Explanation: Pressure head = Pressure / (ρg), unit is meter.
Q18. The SI unit of frequency is
A) Cycle/sec
B) Hertz
C) Rad/sec
D) RPS
Answer: B) Hertz
Explanation: 1 Hertz = 1 cycle per second.
Q19. The SI unit of angular acceleration is
A) rad/s²
B) rev/s²
C) degree/s²
D) rad/s
Answer: A) rad/s²
Explanation: Rate of change of angular velocity with time.
Q20. The SI unit of stress is
A) N/m
B) N/m²
C) N/cm²
D) Pa/s
Answer: B) N/m²
Explanation: Stress = Force / Area = Pascal.
Q21. The SI unit of strain is
A) N/m²
B) No unit
C) m/m
D) m²
Answer: B) No unit
Explanation: Strain is the ratio of change in length to original length, hence dimensionless.
Q22. The SI unit of modulus of elasticity is
A) N/m
B) N/m²
C) N/cm²
D) Joule
Answer: B) N/m²
Explanation: Modulus of elasticity = Stress / Strain = Pascal (Pa).
Q23. The SI unit of impulse is
A) N·s
B) kg·m/s²
C) Joule
D) Watt
Answer: A) N·s
Explanation: Impulse = Force × Time = N·s.
Q24. The SI unit of moment of inertia is
A) kg·m²
B) N·m²
C) kg/m²
D) m⁴
Answer: A) kg·m²
Explanation: Moment of inertia = Mass × (Radius of gyration)².
Q25. The SI unit of angular momentum is
A) N·m
B) kg·m²/s
C) N·s
D) Joule
Answer: B) kg·m²/s
Explanation: Angular momentum = Moment of inertia × Angular velocity.
Q26. The SI unit of power is
A) Watt
B) Joule
C) Calorie
D) Erg
Answer: A) Watt
Explanation: Power = Work / Time = Joule/second.
Q27. The SI unit of mechanical efficiency is
A) Percentage
B) No unit
C) Ratio
D) All of these
Answer: D) All of these
Explanation: Efficiency = Output/Input (dimensionless), often expressed as a percentage.
Q28. The SI unit of gravitational constant (G) is
A) N·m²/kg²
B) N/kg²
C) N·m/kg
D) m²/s²
Answer: A) N·m²/kg²
Explanation: From Newton’s law of gravitation, F = G(m₁m₂)/r².
Q29. The SI unit of weight is
A) Kilogram
B) Newton
C) Gram
D) Dyne
Answer: B) Newton
Explanation: Weight = Mass × Gravity = kg·m/s² = N.
Q30. The SI unit of potential energy is
A) Watt
B) Joule
C) Erg
D) Newton
Answer: B) Joule
Explanation: Potential energy = mgh = Joule.
Q31. The SI unit of kinetic energy is
A) Joule
B) Erg
C) Calorie
D) Newton
Answer: A) Joule
Explanation: Kinetic energy = ½mv² = kg·m²/s² = Joule.
Q32. The SI unit of surface tension is
A) N/m
B) N/m²
C) N/m³
D) kg/m
Answer: A) N/m
Explanation: Surface tension = Force per unit length.
Q33. The CGS unit of surface tension is
A) Dyne/cm
B) Dyne/cm²
C) Erg/cm²
D) Barye
Answer: A) Dyne/cm
Explanation: Surface tension = Force per unit length in CGS system.
Q34. The SI unit of viscosity is
A) Pascal second (Pa·s)
B) N·s/m²
C) Both A and B
D) Dyne·s/cm²
Answer: C) Both A and B
Explanation: Dynamic viscosity = shear stress / rate of strain = Pa·s.
Q35. The CGS unit of viscosity is
A) Poise
B) Dyne·s/cm²
C) Both A and B
D) Barye
Answer: C) Both A and B
Explanation: 1 Poise = 1 Dyne·s/cm² = 0.1 Pa·s.
Q36. The SI unit of kinematic viscosity is
A) m²/s
B) cm²/s
C) Poise
D) Stokes
Answer: A) m²/s
Explanation: Kinematic viscosity = Dynamic viscosity / Density.
Q37. The CGS unit of kinematic viscosity is
A) Stokes
B) Poise
C) cm²/s
D) Both A and C
Answer: D) Both A and C
Explanation: 1 Stokes = 1 cm²/s.
Q38. The SI unit of heat is
A) Joule
B) Calorie
C) Erg
D) Watt
Answer: A) Joule
Explanation: Heat and work have the same unit, Joule.
Q39. The CGS unit of heat is
A) Calorie
B) Erg
C) Joule
D) Dyne
Answer: A) Calorie
Explanation: 1 Calorie = 4.186 Joules.
Q40. The SI unit of temperature is
A) Celsius
B) Kelvin
C) Fahrenheit
D) Rankine
Answer: B) Kelvin
Explanation: Kelvin is the absolute SI unit of temperature.
Q41. The SI unit of charge is
A) Coulomb
B) Ampere
C) Volt
D) Ohm
Answer: A) Coulomb
Explanation: 1 Coulomb = Charge transferred by 1 Ampere current in 1 second.
Q42. The SI unit of current is
A) Ampere
B) Coulomb
C) Volt
D) Watt
Answer: A) Ampere
Explanation: Ampere is the base SI unit of electric current.
Q43. The SI unit of voltage is
A) Watt
B) Volt
C) Ampere
D) Joule
Answer: B) Volt
Explanation: 1 Volt = 1 Joule/Coulomb.
Q44. The SI unit of resistance is
A) Ohm
B) Siemens
C) Volt
D) Coulomb
Answer: A) Ohm
Explanation: Resistance = Voltage / Current.
Q45. The SI unit of electrical power is
A) Joule
B) Volt
C) Watt
D) Ampere
Answer: C) Watt
Explanation: Power = Voltage × Current = Watt.
Q46. The SI unit of capacitance is
A) Farad
B) Henry
C) Weber
D) Coulomb
Answer: A) Farad
Explanation: Capacitance = Charge / Potential difference.
Q47. The SI unit of magnetic flux is
A) Weber
B) Tesla
C) Henry
D) Coulomb
Answer: A) Weber
Explanation: Magnetic flux = B × A = Weber.
Q48. The SI unit of magnetic field intensity is
A) Tesla
B) Weber/m²
C) Both A and B
D) Gauss
Answer: C) Both A and B
Explanation: 1 Tesla = 1 Weber/m².
Q49. The CGS unit of magnetic field is
A) Gauss
B) Tesla
C) Weber
D) Henry
Answer: A) Gauss
Explanation: 1 Tesla = 10⁴ Gauss.
Q50. The SI unit of luminous intensity is
A) Candela
B) Lux
C) Lumen
D) Watt
Answer: A) Candela
Explanation: Candela is the base SI unit of luminous intensity.
Q51. The SI unit of mass moment of inertia is
A) kg·m²
B) N·m²
C) kg/m²
D) Joule
Answer: A) kg·m²
Explanation: Moment of inertia = Mass × (Distance)².
Q52. The SI unit of linear momentum is
A) kg·m/s
B) N·m
C) N·s
D) Both A and C
Answer: D) Both A and C
Explanation: Momentum = Mass × Velocity = kg·m/s = N·s.
Q53. The SI unit of angular momentum is
A) kg·m²/s
B) N·m/s
C) Joule
D) Watt
Answer: A) kg·m²/s
Explanation: Angular momentum = I × ω (moment of inertia × angular velocity).
Q54. The SI unit of torque is
A) N·m
B) N/m
C) N·s
D) Joule
Answer: A) N·m
Explanation: Torque = Force × Perpendicular distance.
Q55. The SI unit of couple is
A) N·m
B) Joule
C) N·s
D) N/m²
Answer: A) N·m
Explanation: Couple = Force × Arm length, same unit as torque.
Q56. The SI unit of work done by a couple is
A) N·m
B) Joule
C) kg·m²/s²
D) Both A and B
Answer: D) Both A and B
Explanation: Work done = Moment × Angular displacement = Joule.
Q57. The SI unit of power developed by a rotating shaft is
A) Watt
B) N·m/s
C) Joule/s
D) All of these
Answer: D) All of these
Explanation: Power = Torque × Angular velocity = N·m/s = Watt.
Q58. The SI unit of modulus of rigidity is
A) N/m²
B) N/m
C) N/m³
D) N
Answer: A) N/m²
Explanation: Shear stress / Shear strain = Modulus of rigidity = Pascal.
Q59. The SI unit of bulk modulus is
A) N/m²
B) N/m
C) N/m³
D) N
Answer: A) N/m²
Explanation: Bulk modulus = Volumetric stress / Volumetric strain.
Q60. The SI unit of linear momentum change rate is
A) Newton
B) Joule
C) Watt
D) kg·m/s²
Answer: A) Newton
Explanation: Force = Rate of change of momentum = kg·m/s² = N.
Q61. The SI unit of linear acceleration is
A) m/s
B) m/s²
C) m²/s
D) cm/s²
Answer: B) m/s²
Explanation: Acceleration = Change in velocity / Time.
Q62. The SI unit of angular acceleration is
A) rad/s²
B) rad/s
C) m/s²
D) rev/s²
Answer: A) rad/s²
Explanation: Rate of change of angular velocity per unit time.
Q63. The SI unit of centroidal distance is
A) Meter
B) Millimeter
C) Centimeter
D) All of these
Answer: D) All of these
Explanation: Centroidal distance is a measure of length.
Q64. The SI unit of moment (first moment of area) is
A) m³
B) m⁴
C) m²
D) m⁵
Answer: A) m³
Explanation: First moment of area = Area × Distance = m² × m = m³.
Q65. The SI unit of second moment of area (moment of inertia of area) is
A) m³
B) m⁴
C) m²
D) m⁵
Answer: B) m⁴
Explanation: I = ∫y² dA, so m² × m² = m⁴.
Q66. The SI unit of bending stress is
A) N/m
B) N/m²
C) N/m³
D) N·m
Answer: B) N/m²
Explanation: Stress = Force / Area = Pascal.
Q67. The SI unit of shear force is
A) Newton
B) Joule
C) N/m²
D) Pascal
Answer: A) Newton
Explanation: Shear force is measured in Newtons.
Q68. The SI unit of bending moment is
A) N/m²
B) N/m
C) N·m
D) N/m³
Answer: C) N·m
Explanation: Bending moment = Force × Distance.
Q69. The SI unit of strain energy is
A) Joule
B) N·m
C) Both A and B
D) Erg
Answer: C) Both A and B
Explanation: Strain energy = Work done by internal forces = Joule.
Q70. The SI unit of angular velocity is
A) rad/s
B) rev/s
C) degree/s
D) rpm
Answer: A) rad/s
Explanation: Angular velocity = Angular displacement / Time.
Q71. The SI unit of displacement is
A) Meter
B) Centimeter
C) Millimeter
D) All of these
Answer: D) All of these
Explanation: Displacement is a measure of length.
Q72. The SI unit of force per unit length is
A) N/m
B) N/m²
C) N·m
D) N/s
Answer: A) N/m
Explanation: Used in tension of cables and surface tension.
Q73. The SI unit of pressure head is
A) Meter
B) Pascal
C) N/m²
D) N/m
Answer: A) Meter
Explanation: Pressure head = Pressure / (ρg), measured in meters.
Q74. The SI unit of mechanical advantage is
A) No unit
B) N/m
C) N/m²
D) Meter
Answer: A) No unit
Explanation: Ratio of output force to input force, hence dimensionless.
Q75. The SI unit of velocity ratio is
A) No unit
B) m/s
C) m/m
D) N/m
Answer: A) No unit
Explanation: Ratio of distance moved by effort to distance moved by load.
Q76. The SI unit of effort efficiency is
A) No unit
B) Watt
C) Joule
D) Pascal
Answer: A) No unit
Explanation: Efficiency = (Output/Input) × 100.
Q77. The SI unit of specific weight is
A) N/m³
B) N/m²
C) N·m
D) kg/m³
Answer: A) N/m³
Explanation: Specific weight = Weight / Volume.
Q78. The SI unit of specific gravity is
A) No unit
B) N/m³
C) kg/m³
D) m/s²
Answer: A) No unit
Explanation: It is a ratio, so dimensionless.
Q79. The SI unit of mechanical work done against gravity is
A) Joule
B) Watt
C) Newton
D) Pascal
Answer: A) Joule
Explanation: Work = Force × Distance = N·m = Joule.
Q80. The SI unit of tractive effort is
A) Newton
B) Joule
C) Watt
D) kgf
Answer: A) Newton
Explanation: Tractive effort is a type of force used to overcome resistance to motion.
 – 80+ Engineering Mechanics MCQs with Answers and Explanations | PATHSHALABASE){kind=link}