{ "correct_letter": "B", "correct_formula": "ΣM_ext = 0", "annotation": "Environment: g=9.81, F_drag=!=0", "choices": [ "ΣF = m·Δv / (Δt·cosθ)", "ΣM_ext = 0", "W = ΔE_k = (1/2)·m·v_t² - (1/2)·m·v_0²", "v = f·λ" ], "correct_index": 1, "physics_type": "AtRest", "seed": "AtRest|NewtonsFirstLaw/AtRest/1", "is_realworld": true, "dropped_wrong_formulas": [ "F_drag = (1/2)·C_d·ρ·A·v²" ] }