A Levels Physics (9702)•9702/11/M/J/22
Explanation
Energy conservation with friction on a ramp Steps:
- Identify the decrease in gravitational potential energy as 35 J (lost as the box slides down).
- Calculate the change in kinetic energy: KE at Y (54 J) minus KE at X (24 J) = 30 J gain.
- Apply conservation of energy: lost PE equals gain in KE plus work done against friction.
- Solve for work against friction: 35 J - 30 J = 5 J.
Why A is correct:
- The work done against friction equals the potential energy lost minus the kinetic energy gained, per the work-energy principle.
Why the others are wrong:
- B: Subtracts initial KE from PE loss (35 J - 24 J = 11 J, ignores final KE).
- C: Adds initial KE to PE loss (24 J + 35 J = 59 J, overestimates total energy).
- D: Adds PE loss to KE gain (35 J + 30 J = 65 J, confuses energy inputs).
Final answer: A
Topic: Energy conservation
Practice more A Levels Physics (9702) questions on mMCQ.me