The joule is equivalent to?

Analyze the question: We need the joule written in base SI units (kg, m, s).

Concept: The joule is the unit of energy and work. Work = Force × Distance.

Solution:

1. Force = mass × acceleration, so the newton is N = kg × m s⁻² = kg m s⁻²

2. Work (energy) = Force × distance, so J = N × m = (kg m s⁻²) × m = kg m² s⁻²

Checking the other options:

• A. kg m² s⁻¹ is the unit of angular momentum (or energy × time), not energy.
• B. kg² m s⁻² has mass squared, which does not match any energy formula.
• D. kg m s⁻¹ is the unit of momentum (or impulse, N s).

You can also verify with kinetic energy, KE = ½mv². Its units are kg × (m s⁻¹)² = kg m² s⁻², which matches option C.

Tip: Build units step by step: force (N) = kg m s⁻², then energy (J) = N × m, power (W) = J/s = kg m² s⁻³. Remember that J = N·m, and the answer follows quickly.