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[
  {
    "slide": 1,
    "fragments": [
      {
        "fragment_index": -1,
        "text_description": "Let’s Meet Friction\nWhere surfaces meet, motion meets resistance.",
        "image_description": ""
      }
    ]
  },
  {
    "slide": 2,
    "fragments": [
      {
        "fragment_index": 1,
        "text_description": "What is Friction?",
        "image_description": ""
      },
      {
        "fragment_index": 2,
        "text_description": "Friction",
        "image_description": ""
      },
      {
        "fragment_index": 3,
        "text_description": "Friction is a contact force that opposes the relative motion, or the tendency to move, between two surfaces in contact.\nCause: Microscopic roughness makes the surfaces interlock, generating the resisting force. Quick check—slide your palm across the desk; which contact force pushes back?",
        "image_description": ""
      }
    ]
  },
  {
    "slide": 3,
    "fragments": [
      {
        "fragment_index": -1,
        "text_description": "Static vs Kinetic",
        "image_description": ""
      },
      {
        "fragment_index": 1,
        "text_description": "",
        "image_description": "https://asset.sparkl.ac/pb/sparkl-vector-images/img_ncert/va9FCDQTW0jh5tmw0xgLL5.png"
      },
      {
        "fragment_index": 2,
        "text_description": "Static vs Kinetic Friction\nWhen you push a resting crate, friction first matches your effort and keeps it still.\nOnce the crate slides, a weaker but steady friction resists its motion.",
        "image_description": ""
      },
      {
        "fragment_index": 3,
        "text_description": "Key Points:\nStatic friction: variable, equals applied force up to \\(f_s^{\\text{max}}\\).\nKinetic friction: constant \\(f_k\\) after motion starts, and \\(f_k < f_s^{\\text{max}}\\).\nDirection: always opposite to intended or actual motion.",
        "image_description": ""
      }
    ]
  },
  {
    "slide": 4,
    "fragments": [
      {
        "fragment_index": -1,
        "text_description": "Laws of Friction",
        "image_description": ""
      },
      {
        "fragment_index": 1,
        "text_description": "\\[f_s \\le \\mu_s N,\\; \\qquad f_k = \\mu_k N\\]\n(with \\(\\mu_k < \\mu_s\\))",
        "image_description": ""
      },
      {
        "fragment_index": 2,
        "text_description": "Variable Definitions\n\\(f_s\\)\nstatic friction force\n\\(f_k\\)\nkinetic friction force\n\\(\\mu_s\\)\ncoefficient of static friction\n\\(\\mu_k\\)\ncoefficient of kinetic friction\n\\(N\\)\nnormal reaction force",
        "image_description": ""
      },
      {
        "fragment_index": 3,
        "text_description": "Applications\nPredict Motion Start\nCompare applied force with \\(f_s^{max} = \\mu_s N\\) to see if the body moves.\nCalculate Sliding Force\nUse \\(f_k\\) to find net force and acceleration once motion begins.\nDesign Safety\nSelect high-\\(\\mu_s\\) materials for better grip in tyres and shoes.",
        "image_description": ""
      }
    ]
  },
  {
    "slide": 5,
    "fragments": [
      {
        "fragment_index": -1,
        "text_description": "Friction vs Load",
        "image_description": ""
      },
      {
        "fragment_index": 1,
        "text_description": "Graph of limiting static friction (F\nlim\n) versus normal force (N)",
        "image_description": "https://asset.sparkl.ac/pb/sparkl-vector-images/img_ncert/NKNKridIlgakcy8oCjOvT4YiI6a1b6GfxmnUYG4V.png"
      },
      {
        "fragment_index": 2,
        "text_description": "Graphical insight\nThe straight line starts at the origin, so limiting static friction \\(F_{\\text{lim}}\\) is zero when normal force \\(N\\) is zero.\nSlope of the line equals coefficient of static friction: \\( \\mu_s = \\frac{F_{\\text{lim}}}{N} \\).",
        "image_description": ""
      },
      {
        "fragment_index": 3,
        "text_description": "Key Points:\nLinear graph shows direct proportionality \\(F_{\\text{lim}} \\propto N\\).\nDouble \\(N\\) ⇒ double \\(F_{\\text{lim}}\\).\nGradient gives \\( \\mu_s \\), a constant for the contact pair.",
        "image_description": ""
      }
    ]
  },
  {
    "slide": 6,
    "fragments": []
  },
  {
    "slide": 7,
    "fragments": [
      {
        "fragment_index": -1,
        "text_description": "Key Takeaways\nQuick recap before practice problems.",
        "image_description": ""
      },
      {
        "fragment_index": 1,
        "text_description": "🖐️\nContact force\nActs only when two surfaces are in contact.",
        "image_description": ""
      },
      {
        "fragment_index": 2,
        "text_description": "🛑\nStatic first\nStatic friction self-adjusts up to \\( \\mu_s N \\) to block motion.",
        "image_description": ""
      },
      {
        "fragment_index": 3,
        "text_description": "➡️\nKinetic next\nOnce motion starts, kinetic friction stays \\( \\mu_k N \\) with \\( \\mu_k < \\mu_s \\).",
        "image_description": ""
      },
      {
        "fragment_index": 4,
        "text_description": "📈\nProportional\nMagnitude of friction is directly proportional to normal reaction \\( N \\).",
        "image_description": ""
      },
      {
        "fragment_index": 5,
        "text_description": "🎮\nControl factors\nChanging surface pair \\( \\mu \\) or load \\( N \\) alters frictional limits.",
        "image_description": ""
      }
    ]
  }
]