{
  "correct_letter": "B",
  "correct_formula": "e = (v_2f - v_1f) / (v_1i - v_2i)",
  "annotation": "Environment: g=9.81, F_drag=!=0\nGround: e=0.5\nBaseball: d = 0.07, e = 0.55, m = 0.14, h = 0.77, v_0 = 0.0\nSteelBall: d = 0.04, e = 0.6, m = 0.26, h = 0.77, v_0 = 0.63",
  "choices": [
    "T = 2π·√(m/k)",
    "e = (v_2f - v_1f) / (v_1i - v_2i)",
    "R = v_0²·sin(2θ) / (g·cos²θ)",
    "σ = F/a² = E·ε"
  ],
  "correct_index": 1,
  "physics_type": "Composition",
  "composition_sources": [
    "InelasticCollision",
    "Projectile"
  ],
  "choice_sources": [
    "InelasticCollision",
    "InelasticCollision",
    "Projectile",
    "InelasticCollision"
  ],
  "seed": "Composition|Composition/3",
  "is_realworld": true,
  "dropped_wrong_formulas": [
    "InelasticCollision: W_f = ∫ μ_k·m·g·ds = ΔE_k",
    "Projectile: F_drag = (1/2)·C_d·ρ·A·v² (A = π·(d/2)²)"
  ]
}