Executive Difficulty Verdict

The January 2024 suite presents a balanced but challenging test of IAS Physics. Unit 1 features a demanding multi-part moments question on a uniform door, which required precise spatial reasoning and trigonometric resolution. Unit 2 pushes conceptual limits with thermistor circuit analyses and solar cell parallel/series power dissipation deductions. Unit 3 demands clean graph plotting and robust uncertainty propagation calculations, reflecting a high expectation for practical skill execution.

Where the Marks Lie

Marks are heavily concentrated in analytical resolution and algebraic manipulation:

  • Mechanics: Resolving projectile motion, analyzing vertical forces on hanging structures, and formulating equations of motion for non-constant acceleration.
  • Materials: Stokes' law calculations, and graphical determination of the Young modulus for brass.
  • Waves & Light: Total internal reflection threshold calculations, standing wave harmonics on strings, and double-gap interference paths.
  • Circuits: Internal resistance investigations, non-ohmic wire resistance variations at elevated temperatures, and solar cell network calculations.

Key Examiner Pitfalls

Examiners highlighted several persistent weaknesses across the candidate cohort:

  • Hysteresis Graph Analysis: Many candidates failed to realize that the heat dissipated corresponds to the area between the loading and unloading curves, or struggled to accurately compute the energy scale of a single grid square.
  • Fluid Dynamics: In terminal velocity problems, candidates frequently omitted either the upthrust of the fluid or the viscous drag force in their force-balance equations.
  • Moment Calculations: Candidates often forgot that the weight of a uniform door acts exactly at \( w/2 \), leading to incorrect clockwise/anticlockwise balancing.
  • Uncertainty Propagation: Halving the range to find absolute uncertainty was frequently missed when processing multiple experimental trials.

Strategy & Prep Recommendations

To maximize scores in subsequent sessions, students should focus on:

  • Practicing three-force equilibrium diagrams and moments about arbitrary pivots.
  • Mastering the potential divider equation and parallel cell rules where internal resistance is non-negligible.
  • Reviewing Huygens' construction mechanics for predicting wave diffraction profiles step-by-step.