NECO 2003 Physics · Question 20

For which of the following sets are the units fundamental?

Options

A.Area, length and volume
B.Impulse, mass and time
C.Length, time and mass
D.Velocity, distance and time
E.Volume, mass and density

Answer: C. Length, time and mass

Explanation written with AI and checked against the answer key

Step 1: Analyze the question The question asks which set contains only fundamental units. Fundamental (base) quantities are those that cannot be expressed in terms of other quantities. Derived quantities are built by combining fundamental ones.

Step 2: Concept The fundamental quantities in the SI system are:

Length (metre, m)
Mass (kilogram, kg)
Time (second, s)
Electric current (ampere, A)
Temperature (kelvin, K)
Amount of substance (mole, mol)
Luminous intensity (candela, cd)

Step 3: Check each option

A. Area, length, volume: Area (m²) and volume (m³) are derived from length. ✗
B. Impulse, mass, time: Impulse (force × time, N·s) is derived. ✗
C. Length, time, mass: All three are base quantities. ✓
D. Velocity, distance, time: Velocity (m/s) is derived. ✗
E. Volume, mass, density: Volume and density (kg/m³) are derived. ✗

Step 4: Answer Only option C has all three quantities as fundamental.

Exam tip: Remember the mechanics trio L-M-T (Length, Mass, Time). If an option includes anything with "per" or a combination, such as velocity, area, density, or force, it is derived, so you can eliminate it quickly.

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