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        "text": "## 单摆周期 · 多周期计时\n摆长 1.00 m，摆球 0.20 kg，初始摆角 8°。",
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            "name": "speed",
            "label": "水平速度 vₓ / (m/s)",
            "expression": "ref_1_ball_vx",
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          },
          {
            "id": "reading_mass",
            "name": "mass",
            "label": "摆球质量 m / kg",
            "expression": "ref_1_basic_mass",
            "visible": true
          },
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            "id": "reading_length",
            "name": "length",
            "label": "支点到球心 L / m",
            "expression": "sqrt((ref_1_basic_x - 1.4583333333333333)^2 + (ref_1_basic_y - 0.7291666666666666)^2)",
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