EXAM YEAR 2026
Q100. Which of these is a derived SI unit rather than an SI base unit?
[DSSSB MTS – 25 July 2026]
A. Ampere
B. Coulomb
C. Metre
D. Kilogram
Answer: B. Coulomb
Explanation: The coulomb is the derived unit of electric charge. Charge equals current multiplied by time, so one coulomb is one ampere-second. Ampere, metre and kilogram are among the seven independent base units of the International System of Units.
Q99. Which correctly pairs the SI unit of work or energy with its dimensional formula?
[RRB NTPC Undergraduate – 19 June 2026]
A. Pascal — [ML⁻¹T⁻²]
B. Joule — [ML²T⁻²]
C. Newton — [MLT⁻²]
D. Watt — [ML²T⁻³]
Answer: B. Joule — [ML²T⁻²]
Explanation: Work is force multiplied by displacement. Since force has dimensions [MLT⁻²], multiplication by length gives [ML²T⁻²]. Its SI unit is the joule. Pascal expresses pressure, newton expresses force, and watt measures power.
Q98. One metric tonne is equal to how many kilograms?
[RRB NTPC Undergraduate – 15 June 2026]
A. 100,000 kg
B. 10,000 kg
C. 1,000 kg
D. 100 kg
Answer: C. 1,000 kg
Explanation: The metric tonne is a commonly used decimal unit of mass equivalent to one thousand kilograms. It is distinct from force or weight, whose SI unit is the newton. Thus converting tonne to kilogram requires multiplication by 1,000.
Q97. A kilowatt-hour is generally used to measure which physical quantity?
[RRB NTPC Undergraduate – 15 June 2026]
A. Electric charge
B. Electric current
C. Electrical energy
D. Force
Answer: C. Electrical energy
Explanation: A kilowatt-hour combines power and time, giving energy. One kilowatt-hour is energy consumed by a one-kilowatt appliance operating for one hour, and equals 3.6 million joules. Electricity bills usually record consumption in these units.
Q96. Which expression gives the SI unit of pressure?
[RRB NTPC Undergraduate – 9 May 2026]
A. Newton per square metre
B. Square metre per newton
C. Newton per metre
D. Newton-metre
Answer: A. Newton per square metre
Explanation: Pressure is the normal force applied per unit area. Therefore its SI unit is N/m², also named the pascal. The dimensions are [ML⁻¹T⁻²]. A newton-metre instead represents a moment of force or an energy value.
Q95. What is the SI base unit of thermodynamic temperature?
[RRB NTPC Graduate – 25 March 2026]
A. Degree Celsius
B. Degree Rankine
C. Kelvin
D. Degree Fahrenheit
Answer: C. Kelvin
Explanation: The kelvin, symbol K, is the fundamental SI unit for thermodynamic temperature. Although Celsius is widely used in daily life, thermodynamic equations use absolute temperatures in kelvin. A temperature change of one kelvin equals one degree Celsius.
Q94. Which is the SI unit of the universal gravitational constant?
[RRB Technician – 10 March 2026]
A. N·m²·kg⁻²
B. N·m⁻²·kg²
C. N·m⁻²·kg⁻¹
D. N·m²·kg⁻¹
Answer: A. N·m²·kg⁻²
Explanation: Newton’s law of gravitation states F = Gm₁m₂/r². Rearrangement gives G = Fr²/(m₁m₂). Substituting SI units for force, distance and masses yields N m² kg⁻², equivalent to m³ kg⁻¹ s⁻².
Q93. Which SI base-unit combination represents one newton of force?
[RRB Technician – 9 March 2026]
A. kg·m·s⁻²
B. Joule
C. Newton-metre
D. kg·m·s⁻¹
Answer: A. kg·m·s⁻²
Explanation: From Newton’s second law, F = ma. Mass is measured in kilograms and acceleration in metres per second squared. Hence one newton equals one kg m s⁻². The last expression, kg m s⁻¹, denotes momentum.
Q92. Which SI unit is used for the weight of a body?
[RRB Group D – 10 February 2026]
A. Kilogram
B. Newton
C. Pascal
D. Joule
Answer: B. Newton
Explanation: Weight is the gravitational force exerted on a body, expressed as W = mg. Consequently its SI unit is the newton. A kilogram measures mass, while pascal describes pressure and joule describes energy or mechanical work.
Q91. What is the SI unit used to express average speed?
[RRB Group D – 9 February 2026]
A. Kilometre per hour
B. Metre per second squared
C. Centimetre per second
D. Metre per second
Answer: D. Metre per second
Explanation: Average speed is total distance covered divided by total elapsed time. The SI unit is therefore metre per second because length uses metres and time uses seconds. Kilometres per hour and centimetres per second are valid but non-SI presentations.