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[
{
"slide": 1,
"fragments": [
{
"fragment_index": -1,
"text_description": "Why Don’t We Slip Walking?\nFriction – the hidden grip under every step.",
"image_description": ""
}
]
},
{
"slide": 2,
"fragments": [
{
"fragment_index": -1,
"text_description": "Quick Check\nSubmit Answer\nCorrect!\nYes—static friction grips the sole and stops backward slip.\nIncorrect\nReview what force acts just before the foot starts to move.\nconst correctOption = 0;\n const answerCards = document.querySelectorAll('.answer-card');\n const submitBtn = document.getElementById('submitBtn');\n const feedbackCorrect = document.getElementById('feedbackCorrect');\n const feedbackIncorrect = document.getElementById('feedbackIncorrect');\n \n let selectedOption = null;\n \n answerCards.forEach((card, index) => {\n card.addEventListener('click', () => {\n answerCards.forEach(c => c.classList.remove('border-blue-500', 'bg-blue-50'));\n card.classList.add('border-blue-500', 'bg-blue-50');\n selectedOption = index;\n });\n });\n \n submitBtn.addEventListener('click', () => {\n if (selectedOption === null) return;\n \n if (selectedOption === correctOption) {\n feedbackCorrect.classList.remove('hidden');\n feedbackIncorrect.classList.add('hidden');\n } else {\n feedbackIncorrect.classList.remove('hidden');\n feedbackCorrect.classList.add('hidden');\n }\n });",
"image_description": ""
},
{
"fragment_index": 1,
"text_description": "Question\nWhich force prevents your foot from sliding backward as you walk?",
"image_description": ""
},
{
"fragment_index": 2,
"text_description": "1\nStatic friction",
"image_description": ""
},
{
"fragment_index": 3,
"text_description": "2\nKinetic friction",
"image_description": ""
},
{
"fragment_index": 4,
"text_description": "3\nGravity",
"image_description": ""
},
{
"fragment_index": 5,
"text_description": "4\nNormal force",
"image_description": ""
},
{
"fragment_index": 6,
"text_description": "Hint:\nThink of the force acting before any sliding begins.",
"image_description": ""
}
]
},
{
"slide": 3,
"fragments": [
{
"fragment_index": -1,
"text_description": "Hidden Grip Between Surfaces\nMicroscopic origin of friction\nMagnified contact: jagged peaks interlock and weak atomic bonds form.",
"image_description": ""
},
{
"fragment_index": 1,
"text_description": "Surfaces are never perfectly smooth; even polished metal has tiny peaks and valleys.",
"image_description": ""
},
{
"fragment_index": 2,
"text_description": "These irregular peaks interlock, so micro-joints must break before sliding begins.",
"image_description": ""
},
{
"fragment_index": 3,
"text_description": "Atoms in close contact create weak adhesive bonds, adding extra resistance to motion.",
"image_description": ""
}
]
},
{
"slide": 4,
"fragments": [
{
"fragment_index": 1,
"text_description": "Definition",
"image_description": ""
},
{
"fragment_index": 2,
"text_description": "Static Friction",
"image_description": ""
},
{
"fragment_index": 3,
"text_description": "Static friction is the force that resists the impending motion between two contacting surfaces and keeps them still.\nIt increases up to a maximum, then motion begins.",
"image_description": ""
},
{
"fragment_index": 4,
"text_description": "Source: NCERT Fig.4.10a",
"image_description": ""
}
]
},
{
"slide": 5,
"fragments": [
{
"fragment_index": -1,
"text_description": "Kinetic Friction\nSource: NCERT Fig.4.10b",
"image_description": ""
},
{
"fragment_index": 1,
"text_description": "Kinetic Friction",
"image_description": ""
},
{
"fragment_index": 2,
"text_description": "Kinetic friction is the force that opposes the relative sliding motion between two contacting surfaces once they are in motion.\nIt appears only after motion begins; it is absent while the body remains at rest.",
"image_description": ""
}
]
},
{
"slide": 6,
"fragments": [
{
"fragment_index": -1,
"text_description": "Friction Formulae",
"image_description": ""
},
{
"fragment_index": 1,
"text_description": "\\(f_s \\le \\mu_s N,\\; f_k = \\mu_k N\\)",
"image_description": ""
},
{
"fragment_index": 3,
"text_description": "Static friction rises with push up to its limit \\( \\mu_s N\\). Once motion starts, kinetic friction stays constant at \\( \\mu_k N\\). Both forces scale with the normal force \\(N\\).\n\\(N\\) equals the object’s weight only on a horizontal surface; on an incline, calculate \\(N\\) first.",
"image_description": ""
},
{
"fragment_index": 2,
"text_description": "For most surfaces, \\( \\mu_s \\ge \\mu_k \\).",
"image_description": ""
}
]
},
{
"slide": 7,
"fragments": [
{
"fragment_index": 1,
"text_description": "Static vs Kinetic Friction\nHow do the two types differ?",
"image_description": ""
},
{
"fragment_index": 2,
"text_description": "Static friction\nSurfaces remain at rest.\nVariable up to a limit: \\(F_s \\le \\mu_s N\\).\nUsually larger coefficient \\(\\mu_s\\).",
"image_description": ""
},
{
"fragment_index": 3,
"text_description": "Kinetic friction\nSurfaces slide past one another.\nNearly constant: \\(F_k = \\mu_k N\\).\nSmaller coefficient \\(\\mu_k\\).",
"image_description": ""
},
{
"fragment_index": 4,
"text_description": "Similarities\nBoth oppose motion or its tendency.\nAct parallel to contact surface and depend on normal force \\(N\\).\nZero when contact is lost—pure contact forces.",
"image_description": ""
},
{
"fragment_index": 5,
"text_description": "Tip: Decide direction first; then use \\(\\mu_s\\) or \\(\\mu_k\\) as needed—remember \\(\\mu_s > \\mu_k\\) for most surfaces.",
"image_description": ""
}
]
},
{
"slide": 8,
"fragments": [
{
"fragment_index": -1,
"text_description": "Multiple Choice Question\nSubmit Answer\nCorrect!\nRight! Static friction demands more force to start motion.\nIncorrect\nRemember the first push needs more effort than steady sliding.\n// MCQ interaction logic\n const correctOption = 0;\n const answerCards = document.querySelectorAll('.answer-card');\n const submitBtn = document.getElementById('submitBtn');\n const feedbackCorrect = document.getElementById('feedbackCorrect');\n const feedbackIncorrect = document.getElementById('feedbackIncorrect');\n \n let selectedOption = null;\n \n answerCards.forEach((card, index) => {\n card.addEventListener('click', () => {\n answerCards.forEach(c => c.classList.remove('border-blue-500', 'bg-blue-50'));\n card.classList.add('border-blue-500', 'bg-blue-50');\n selectedOption = index;\n });\n });\n \n submitBtn.addEventListener('click', () => {\n if (selectedOption === null) return;\n \n if (selectedOption === correctOption) {\n feedbackCorrect.classList.remove('hidden');\n feedbackIncorrect.classList.add('hidden');\n } else {\n feedbackIncorrect.classList.remove('hidden');\n feedbackCorrect.classList.add('hidden');\n }\n });",
"image_description": ""
},
{
"fragment_index": 1,
"text_description": "Question\nFor dry wood-on-wood contact, which coefficient is usually larger?",
"image_description": ""
},
{
"fragment_index": 2,
"text_description": "1\n\\( \\mu_s \\)",
"image_description": ""
},
{
"fragment_index": 3,
"text_description": "2\n\\( \\mu_k \\)",
"image_description": ""
},
{
"fragment_index": 4,
"text_description": "3\nBoth equal",
"image_description": ""
},
{
"fragment_index": 5,
"text_description": "4\nCannot say",
"image_description": ""
},
{
"fragment_index": 6,
"text_description": "Hint:\nRecall the extra force needed to start motion.",
"image_description": ""
}
]
},
{
"slide": 9,
"fragments": [
{
"fragment_index": 1,
"text_description": "Block on Incline\nDetermine the angle of repose using the static-friction limit.",
"image_description": ""
},
{
"fragment_index": 2,
"text_description": "1\nDraw forces\nOn the inclined plane show \\(mg\\sin\\theta\\), \\(mg\\cos\\theta\\), normal \\(N\\), and static friction \\(f_s\\) up the slope.",
"image_description": ""
},
{
"fragment_index": 3,
"text_description": "2\nApply static limit\nAt impending slide \\(f_s = \\mu_s N\\). Balance along the plane: \\(mg\\sin\\theta = \\mu_s mg\\cos\\theta\\).",
"image_description": ""
},
{
"fragment_index": 4,
"text_description": "3\nFind angle of repose\nSolve to get \\( \\theta_r = \\tan^{-1}\\mu_s \\). Sliding starts when \\(\\theta \\ge \\theta_r\\).",
"image_description": ""
},
{
"fragment_index": 5,
"text_description": "Remember: the angle of repose links the friction coefficient directly to the slope angle—no mass term appears.",
"image_description": ""
}
]
},
{
"slide": 10,
"fragments": [
{
"fragment_index": 1,
"text_description": "Common Mistakes\nTop mistakes & fixes — avoid friction misconceptions.",
"image_description": ""
},
{
"fragment_index": 2,
"text_description": "Normal force ≠ weight when surface tilts or extra pushes act.",
"image_description": ""
},
{
"fragment_index": 3,
"text_description": "Friction opposes relative motion tendency, not always velocity.",
"image_description": ""
},
{
"fragment_index": 4,
"text_description": "Coefficient \\( \\mu \\) is a ratio and therefore unitless.",
"image_description": ""
},
{
"fragment_index": 5,
"text_description": "Draw \\(N\\) perpendicular to the contact surface.",
"image_description": ""
},
{
"fragment_index": 6,
"text_description": "Decide motion tendency first; set \\(F_f\\) opposite.",
"image_description": ""
},
{
"fragment_index": 7,
"text_description": "Write \\( \\mu = \\frac{F}{N} \\) and watch units cancel.",
"image_description": ""
}
]
},
{
"slide": 11,
"fragments": [
{
"fragment_index": 1,
"text_description": "Friction — Key Takeaways\nRemember these six essential points.",
"image_description": ""
},
{
"fragment_index": 2,
"text_description": "1\nDefinition\nForce that resists sliding between two touching surfaces.",
"image_description": ""
},
{
"fragment_index": 3,
"text_description": "2\nDirection\nAlways opposite to actual or impending motion.",
"image_description": ""
},
{
"fragment_index": 4,
"text_description": "3\nStatic limit\nMaximum static friction \\(F_s^{\\text{max}} = \\mu_s N\\).",
"image_description": ""
},
{
"fragment_index": 5,
"text_description": "4\nKinetic value\nSliding friction \\(F_k = \\mu_k N,\\; \\mu_k < \\mu_s\\).",
"image_description": ""
},
{
"fragment_index": 6,
"text_description": "5\nCoefficient\n\\(\\mu\\) depends only on surface pair, not area or speed.",
"image_description": ""
},
{
"fragment_index": 7,
"text_description": "6\nAngle φ\nLimiting angle: \\(\\tan\\phi = \\mu_s\\); equals angle of repose.",
"image_description": ""
}
]
},
{
"slide": 12,
"fragments": [
{
"fragment_index": -1,
"text_description": "Exit Ticket\nSubmit Answer\nCorrect!\nGreat! You’re set.\nIncorrect\nRework using weight 19.6 N.\nconst correctOption = 0;\n const answerCards = document.querySelectorAll('.answer-card');\n const submitBtn = document.getElementById('submitBtn');\n const feedbackCorrect = document.getElementById('feedbackCorrect');\n const feedbackIncorrect = document.getElementById('feedbackIncorrect');\n \n let selectedOption = null;\n \n answerCards.forEach((card, index) => {\n card.addEventListener('click', () => {\n answerCards.forEach(c => c.classList.remove('border-blue-500', 'bg-blue-50'));\n card.classList.add('border-blue-500', 'bg-blue-50');\n selectedOption = index;\n });\n });\n \n submitBtn.addEventListener('click', () => {\n if (selectedOption === null) return;\n \n if (selectedOption === correctOption) {\n feedbackCorrect.classList.remove('hidden');\n feedbackIncorrect.classList.add('hidden');\n } else {\n feedbackIncorrect.classList.remove('hidden');\n feedbackCorrect.classList.add('hidden');\n }\n });",
"image_description": ""
},
{
"fragment_index": 1,
"text_description": "Question\nA 2 kg block rests on a horizontal floor. What is the maximum static friction force? Given \\( \\mu_s = 0.40 \\).",
"image_description": ""
},
{
"fragment_index": 2,
"text_description": "1\n7.84 N",
"image_description": ""
},
{
"fragment_index": 3,
"text_description": "2\n4.0 N",
"image_description": ""
},
{
"fragment_index": 4,
"text_description": "3\n2.0 N",
"image_description": ""
},
{
"fragment_index": 5,
"text_description": "4\n8.5 N",
"image_description": ""
},
{
"fragment_index": 6,
"text_description": "Hint:\nUse \\(f_{s,\\text{max}} = \\mu_s N\\) and \\(N = mg\\).",
"image_description": ""
}
]
}
]