A Levels Physics (9702)•9702/13/O/N/18

Explanation
Dimensional Analysis of Units Steps:
- Determine dimensional formula for distance: [L].
- Determine dimensional formula for force: [M L T^{-2}].
- Determine dimensional formula for power × time: power is [M L^{2} T^{-3}], multiplied by time [T] gives [M L^{2} T^{-2}].
- Compare exponents of length (L): A, B, and D have L^{1}; C has L^{2}.
Why C is correct:
- Power × time equals energy (from work-energy theorem, W = P t), with dimensional formula [M L^{2} T^{-2}], featuring L^{2} unlike the L^{1} in the others.
Why the others are wrong:
- A: Distance has [L], with L^{1}.
- B: Force has [M L T^{-2}], with L^{1}.
- D: Rate of change of momentum equals force (Newton's second law, F = dp/dt), with [M L T^{-2}] and L^{1}.
Final answer: C
Topic: SI units
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