A Levels Physics (9702)•9702/12/M/J/21

Explanation
Ratio of potential energy gain to work by applied force on incline
Steps:
- Height gained h = s sin α, so gravitational PE gain = m g h = m g s sin α.
- At constant velocity, force F acts parallel to slope, so work by F = F s.
- Ratio = (m g s sin α) / (F s) = m g sin α / F.
- This follows from work-energy theorem, as net work equals PE change.
Why D is correct:
- D equals the derived ratio using PE formula mgh and work W = F s under constant velocity (net force zero, F balances mg sin α component).
Why the others are wrong:
- A: Identical to D, but listed as distractor; correct form is D.
- B: Involves velocity v, irrelevant to energy ratio without kinetic change.
- C: Simplifies to F/(2s), resembling kinetic energy formula but ignores gravity and constant speed.
Final answer: D
Topic: Gravitational potential energy and kinetic energy
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