Difficulty Verdict: A Fair but Rigorous Examination

The October/November 2025 AS Level Physics papers (9702/11, 21, and 31) represent a well-balanced assessment of the Cambridge syllabus. Paper 11 maintained a standard difficulty profile with some challenging questions on wave polarization and Doppler effect. Paper 21 placed a significant emphasis on algebraic derivations—such as showing that the spring constant of a wire is given by \( k_0 = \frac{EA}{L} \)—and demanding unit conversions. Paper 31 required careful physical manipulation, particularly in handling delicate paper cylinders and setting up the dual-spring oscillation apparatus.

Where the Marks Are Loaded

Marks are heavily concentrated in Deformation of Solids and Experimental Physics, largely due to the practical paper weighting. Specifically, the paper deformation investigation in Paper 31, combined with the Young Modulus calculations in Paper 21, accounted for nearly 18% of the total available marks. Kinematics, Work, Energy, and Power, and Practical Circuits also carried substantial weight, particularly through multi-step calculation questions like finding the average power output of a rocket engine and evaluating parallel thermistor networks.

Examiner Pitfalls & Lost Opportunities

Analysis of student performance reveals common areas where high-achieving candidates drop easy marks:

  • Viscosity Unit Derivation: In Paper 21, Question 2, deriving the SI base units for viscosity \( \eta \) tripped up many. Candidates forgot that the base units of force are \( \text{kg}\cdot\text{m}\cdot\text{s}^{-2} \), leading to algebraic errors.
  • Circuit Explanations: Explaining why the current in resistor \( R \) decreases as the thermistor's temperature rises proved difficult. Many candidates failed to articulate that a lower thermistor resistance increases the overall circuit current, which in turn increases the potential difference across the cell's internal resistance, thereby lowering the terminal potential difference.
  • Significant Figures in Practicals: In Paper 31, failing to justify the significant figures of the constant \( k \) by linking it directly to the raw measurements of width \( w \) and extension \( (y-p) \) was a major source of lost marks.

Strategy for Success & Next-Step Predictions

To excel in future sessions, candidates must focus heavily on core algebraic manipulation and systematic unit analysis. Never treat "show that" questions lightly; examiners look for explicit substitution of values before final answers are written. For the upcoming series, we predict a strong return of Potential Dividers and Stationary Waves on a String, as these topics were under-represented in the structured questions here. Ensure you practice drawing free-body diagrams with forces originating precisely from the center of gravity of the falling sphere to secure easy marks.